CD8A-Binding Fibronectin Type III Domains

ABSTRACT

Fibronectin type III domains (FN3) that specifically bind to CD8A, related polynucleotides capable of encoding CD8A-specific FN3 domains, cells expressing the FN3 domains, as well as associated vectors, and detectably labeled FN3 domains are useful in therapeutic and diagnostic applications.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application Ser. No. 62/434,017, filed 14 Dec. 2016. The entire contents of the aforementioned application are incorporated herein by reference in its entirety.

SEQUENCE LISTING

The instant application contains a Sequence Listing which has been submitted electronically in ASCII format and is hereby incorporated by reference in its entirety. Said ASCII copy, created on Dec. 5, 2017, is named JBI5112USNP_SL.txt and is 256,587 bytes in size.

TECHNICAL FIELD

The present invention relates to fibronectin type III (FN3) domains that specifically bind to cluster of differentiation 8a (CD8a). Such FN3 domains may be used for example, for medical imaging, diagnostics, and pharmaceutical therapy. Methods for the production of such molecules and diagnostic agents comprising them are also provided.

BACKGROUND

The rapidly evolving fields of cancer immunotherapy have recently led to the FDA approval of several new immunotherapies, with many more therapies presently in clinical trials for a variety of cancers. Furthermore, cellular, small molecule, antibody-based immunotherapies, and combinations thereof, are being rigorously tested preclinically for clinical translation. The dynamic tumor microenvironment and tumor heterogeneity have become important topics in both preclinical and clinical studies (Hanahan D, Weinberg R A. Cell 2011; 144:646-74; M antovani A, Allavena P, Sica A, Balkwill F. Nature 2008; 454:436-44; Schreiber R D, Old L J, Smyth M J. Science 2011; 331:1565-70.), but the ability to monitor changes in the immune status of primary lesions and metastatic cancers is limited. Current methods to monitor lymphocytes from whole blood or biopsies from heterogeneous tumors do not reflect the dynamic and spatial information likely required to monitor immune responses to therapeutic intervention, many of which elicit whole body changes in immune cell numbers and localization. Therefore, molecular imaging methods that can noninvasively monitor both systemic and intratumoral alterations in immune cell numbers or localization during experimental therapies have the ability to increase the understanding of the dynamics of immunotherapeutic mechanism with the potential to provide translatable methods for predicting and/or assessing clinical immunotherapeutic responses.

Analysis of tumor-infiltrating lymphocytes (TIL) has demonstrated the importance of tumor immune microenvironment and that the presence of cytotoxic CD8⁺ T cells can predict overall survival in breast, lung, ovarian, melanoma, and colorectal cancers (reviewed in refs. Pages F, et al., Oncogene 2010; 29:1093-102. and Gooden M J, et al. Br J Cancer 2011; 105:93-103.). With the recent clinical successes of immunotherapies that alter the tumor immune microenvironment, including adoptive cell transfer (ACT) of T-cell receptor (TCR)- or chimeric antigen receptor-transduced cytotoxic T cells (Johnson L A, et al. Blood 2009; 114:535-46; Rosenberg S A. Sci Transl Med 2012; 4:127ps8.), agonistic antibodies targeting CD137 (4-1BB) and CD40 (Melero I, et al. Clin Cancer Res 2013; 19:997-1008; Melero I, et al. Nat Rev Cancer 2007; 7:95-106; Vinay D S, and Kwon B S. Mol Cancer Ther 2012; 11:1062-70.), and antibody blockade of the checkpoint inhibitors CTLA-4, PD-1, and PD-L1 (Callahan M K, and Wolchok J D. J Leukoc Biol 2013; 94:41-53; Shin D S, and Ribas A. Curr Opin Immunol 2015; 33C:23-35; Topalian S L, et al. Cancer Cell 2015; 27:450-61.), the ability to noninvasively monitor the tumor immune response to therapy has become of upmost importance.

SUMMARY

The present invention comprises CD8A-binding fibronectin type III (FN3) domains. Also described are related polynucleotides capable of encoding the provided FN3 domains, cells expressing the provided FN3 domains, as well as associated vectors. In addition, methods of using the provided FN3 domains are described. For example, the FN3 domains of the invention can be used to noninvasively and quantitatively monitor the presence and abundance of CD8+ T cells.

In some embodiments, the present invention comprises isolated FN3 domains, wherein the FN3 domains bind to a human CD8A comprising SEQ ID NO: 35. In other embodiments, the CD8A-specific FN3 domains bind to human CD8A and cynomolgus monkey CD8A. In yet other embodiments, the CD8A-specific FN3 domains are based on Tencon sequence of SEQ ID NO: 1. In further embodiments, the CD8A-specific FN3 domains are based on the Tencon27 sequence of SEQ ID NO: 4. In some embodiments, the albumin-specific FN3 domains are isolated from the library comprising the sequence of SEQ ID NOs: 2, 3, 5, 6, 7 or 8. In some embodiments, the CD8A-specific FN3 domains do not activate CD8+ T-cells in vitro as measured by the enzyme-linked immunospot (ELISPOT) assay. In some embodiments, the CD8A-specific FN3 domains bind human CD8A with an affinity (K_(D)) of between about 0.02 to about 6.6 nM as measured by surface plasmon resonance. In other embodiments, the CD8A-specific FN3 domains have a cysteine substitution at residue position 54 of SEQ ID NOs 79, 81, 83, 89, 122 and 68. In other embodiments, the CD8A-specific FN3 domains comprise the amino acid sequence of SEQ ID NOs: 40-269. In other embodiments, the CD8A-specific FN3 domains are conjugated to a detectable label.

In addition to the described CD8A-specific FN3 domains, also provided are polynucleotide sequences capable of encoding the described FN3 domains. Vectors comprising the described polynucleotides are also provided, as are cells expressing the CD8A-specific FN3 domains herein. Also described are cells capable of expressing the disclosed vectors. These cells may be mammalian cells (such as 293F cells, CHO cells), insect cells (such as Sf7 cells), yeast cells, plant cells, or bacteria cells (such as E. coli). A process for the production of the described FN3 domains is also provided.

The present invention also comprises methods of conjugating or otherwise associating the described CD8A-specific FN3 domains to various molecules for diagnostic purposes. For example, Zr-89 or I-124 are ideal fusion partners for creation of diagnostic agents capable of detecting the presence of CD8+ T-cells. As such, the CD8A-specific FN3 domains have utility in cancer diagnostics using CD8A as a biomarker.

Another embodiment of the invention is a method of detecting CD8A-expressing cells in a biological sample comprising treating the biological sample with a diagnostic agent comprising the described CD8A-specific FN3 domains. These methods are provided in the EXAMPLES.

Within the scope of the invention are kits including the disclosed CD8A-specific FN3 domains. The kits may be used to carry out the methods of using the CD8A-specific FN3 domains provided herein, or other methods known to those skilled in the art. In some embodiments, the described kits may include the FN3 domains described herein and reagents for use in detecting the presence of human CD8A in a biological sample. The described kits may include one or more of the FN3 domains described herein and a vessel for containing the FN3 domains when not in use, instructions for use of the FN3 domains affixed to a solid support, and/or detectably labeled forms of the FN3 domains, as described herein.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A-1D. The CD8S365-DFO conjugate does not activate T cells de novo and does not modulate the antigen dependent activation of T cells in a 24 hour INF EliSpot assay. CMV reactive T cells were treated with 365-DFO in the absence (A) or presence (B) of CMV peptides. A second M1 reactive donor was also tested in the absence (C) or presence (D) of M1 peptides.

FIGS. 2A and 2B. The CD8S365-DFO conjugate does not activate T cells de novo and does not modulate the antigen dependent activation of T cells in a 6 day INF^(γ) MSD assay. CMV reactive T cells were treated with 365-DFO in the absence (A) or presence (B) of CMV peptides.

FIG. 3 . Crude preparatory HPLC trace of [¹²⁴I]-IPEM. Preparatory HPLC was performed using a Waters 1525 Binary HPLC pump, a Waters 2489 dual wavelength UV/Visible Detector (λ=214 and 254 nm), a Bioscan Flow Count radiodetector (B-FC-2000) and a Atlantis T3, 100 Å, 5 μm, 150×4.6 mm HPLC column. The elution profile used was as follows: solvent A=H₂O (0.1% AcOH (v/v)), Solvent B=MeCN (0.1% AcOH (v/v)), flow rate=1.5 mLmin⁻¹; initial=80% A, 20 min=0% A (linear gradient). Multiple small molecule absorbance on UV-vis traces at 254 nm (top graph) and 214 nm (middle graph) indicate presence of impurities and by-products in the crude reaction mixture. Radiotrace (bottom graph) also shows expected baseline peaks due to radiolabeled impurities.

FIG. 4 . Analytical HPLC trace of [¹²⁴I]-IPEM. Analytical HPLC was performed using a Waters 1525 Binary HPLC pump, a Waters 2707 autosampler, a Waters 2489 dual wavelength UV/Visible Detector (λ=214 and 280 nm), a Bioscan Flow Count radiodetector (B-FC-2000) and a Phenomenex Kinetex 5 μm XB-C18 100 Å, 150×4.6 mm HPLC column. The elution profile used was as follows: solvent A=H₂O (0.1% TFA (v/v)), Solvent B=MeCN (0.1% TFA (v/v)), flow rate=1 mLmin⁻¹; initial=90% A, 15 min=0% A (linear gradient). Analytically pure [I-124] IPEM shows a single radiopeak (bottom graph) with a smooth baseline confirming successful purification. Please note that [I-124] IPEM is an organic small molecule; hence, lacking absorption at 280 nm (top graph) and 214 nm (middle graph).

FIG. 5 . Radio TLC of purified [¹²⁴I]-IPEM CD8S365. The iTLC-SG plate (Agilent, cat #SGI0001) was read on a Bioscan AR-2000 radio-TLC imaging scanner. The radio TLC plate (FIG. 3 ) was co-spotted with 1 μL of NaI (0.1 M) and developed using citric acid (0.5 mM, pH=5) as eluent. The origin=20 mm and the solvent front=100 mm. The radio TLC eluent was prepared by dissolving 96 mg of citric acid (Spectrum cat #CI131) in 25 mL of Trace Select H₂O and then Na₂CO₃ was added (245 μL, 2 M); the pH was checked by strip (pH=5).

FIG. 6 . Analytical HPLC trace of purified [¹²⁴I]-IPEM CD8S 365. Analytical HPLC was performed using a Waters 1525 Binary HPLC pump, a Waters 2707 autosampler, a Waters 2489 dual wavelength UV/Visible Detector (λ=214 and 280 nm), a Bioscan Flow Count radiodetector (B-FC-2000) and a Phenomenex Kinetex 5 μm XB-C18 100 Å, 150×4.6 mm HPLC column. The elution profile used was as follows: solvent A=H₂O (0.1% TFA (v/v)), Solvent B=MeCN (0.1% TFA (v/v)), flow rate=1 mLmin⁻¹; initial=90% A, 15 min=0% A (linear gradient). Biomolecule (CD8S) absorbance at 280 nm (top graph) and small molecule (I124-IPEM) absorbance at 214 nm (middle graph) confirms successful conjugation reaction. UV and radio traces (bottom graph) indicate an analytically pure sample.

FIG. 7 . MALDI-MS of IPEM CD8S365 (theoretical MW=10786.12). The MALDI-MS analysis was performed at the Biointerfaces Institute using a Bruker UltrafleXtreme MALDI TOF/TOF in positive ion mode (linear detector). A saturated solution of sinapinic acid was prepared in TA30 solvent (30:70 (v/v) MeCN:0.1% TFA in water). The sample (c=0.397 mgmL⁻¹) was mixed in a 1:1 ratio with the matrix solution and 1 μL was spotted on the plate. A protein solution was used as an external standard.

FIG. 8 . Co-injection of [¹²⁴I]-IPEM CD8S365 with cold standard. Analytical HPLC was performed using a Waters 1525 Binary HPLC pump, a Waters 2707 autosampler, a Waters 2489 dual wavelength UV/Visible Detector (λ=214 and 280 nm), a Bioscan Flow Count radiodetector (B-FC-2000) and a Phenomenex Kinetex 5 μm XB-C18 100 Å, 150×4.6 mm HPLC column. The elution profile used was as follows: solvent A=H₂O (0.1% TFA (v/v)), Solvent B=MeCN (0.1% TFA (v/v)), flow rate=1 mLmin⁻¹; initial=90% A, 15 min=0% A (linear gradient). Co-injection with cold sample leads to complete overlap of UV peaks (top and middle graphs), confirming the product's molecular identity (i.e. Cold and radiolabeled conjugates are identical except for the replacement of Iodine by Iodine-124)

FIG. 9 . Representative PET image showing CD8S365-IPEM5 radiolabeled with I-124, taken at 2 h post-injection. The image is a maximum intensity projection (anterior-posterior), with the spleen centered on the cross-hairs. The organs below the spleen are the kidneys, and the image is oriented to show the head at the top. The uptake in the thyroid is evidence of some de-iodination of the protein.

FIG. 10 . Time-activity curves for blood radioactivity in non-human primate for each anti-CD8A FN3 domain labeled with either Zr-89 or I-124.

FIGS. 11A and 11B. Time-activity curves for organ radioactivity in NHP for each centyrin labeled with either Zr-89 or I-124. FIG. 11A includes kidneys, liver and spleen, while FIG. 11B is focused on the spleen. The 24 h time point for [¹²⁴I]-IPEM CD8S365 is missing due to a technical issue. The high uptake of Zr-89 in kidneys due to residualization of the isotope is largely absent from the I-124 data.

FIG. 12A-12C. Confirmation of CD8 T cell depletion by Day 3 in blood taken from a non-human primate (12A). Also shown are changes in CD4 (12B) and CD3 T cells (12C).

FIG. 13 . Representative PET image showing the 365 anti-CD8A FN3 domain radiolabeled with I-124, taken at 2 h post-injection in a CD8-depleted animal. The image is a maximum intensity projection (anterior-posterior). This is to be compared against the non-depleted animal in FIG. 9 , where the spleen is clearly visible above the kidney.

FIG. 14 . Time-activity curves for blood radioactivity in cynomolgus monkeys for both depleted and non-depleted animals after administration of [¹²⁴I]-IPEM CD8S365.

FIGS. 15A and 15B. Time-activity curves for organ radioactivity in cynomolgus monkeys for both depleted and non-depleted animals. 15A includes kidneys, liver and spleen, while 15B is focused on the spleen.

FIG. 16 . Representative PET image of a two idenitally treated mice showing the CD8S365-IPEM radiolabeled with I-124, taken at 3 h post-injection. The image is a 3D maximum intensity projection, overlaid on a CT scan. Tumor (formed from HEK-293-luc transfected to over-express huCD8+) and other organs are indicated by arrows. The uptake in the thyroid is evidence of some de-iodination of the protein.

FIG. 17 . Time-activity curve for blood radioactivity in mice bearing either HEK-293-luc CD8+ or HEK-293 parental tumors.

FIG. 18 . Time-activity curve for tumor radioactivity in mice bearing either HEK-293-luc CD8+ or HEK-293 parental tumors.

FIG. 19 . Uptake of the I-124 labeled CD8S365 in the HEK293 CD8 overexpressing cells, as a function of the number of implanted cells.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS Definitions

Various terms relating to aspects of the description are used throughout the specification and claims. Such terms are to be given their ordinary meaning in the art unless otherwise indicated. Other specifically defined terms are to be construed in a manner consistent with the definitions provided herein.

As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the content clearly dictates otherwise. Thus, for example, reference to “a cell” includes a combination of two or more cells, and the like.

The term “about” as used herein when referring to a measurable value such as an amount, a temporal duration, and the like, is meant to encompass variations of up to ±10% from the specified value, as such variations are appropriate to perform the disclosed methods. Unless otherwise indicated, all numbers expressing quantities of ingredients, properties such as molecular weight, reaction conditions, and so forth used in the specification and claims are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements.

“Isolated” means a biological component (such as a nucleic acid, peptide or protein) has been substantially separated, produced apart from, or purified away from other biological components of the organism in which the component naturally occurs, i.e., other chromosomal and extrachromosomal DNA and RNA, and proteins. Nucleic acids, peptides and proteins that have been “isolated” thus include nucleic acids and proteins purified by standard purification methods. “Isolated” nucleic acids, peptides and proteins can be part of a composition and still be isolated if such composition is not part of the native environment of the nucleic acid, peptide, or protein. The term also embraces nucleic acids, peptides and proteins prepared by recombinant expression in a host cell as well as chemically synthesized nucleic acids. An “isolated” FN3 domain, as used herein, is intended to refer to an FN3 domain which is substantially free of other FN3 domains having different antigenic specificities (for instance, an isolated FN3 domain that specifically binds to human serum albumin is substantially free of FN3 domains that specifically bind antigens other than human serum albumin). An isolated FN3 domain that specifically binds to an epitope, isoform or variant of human serum albumin may, however, have cross-reactivity to other related antigens, for instance from other species (such as serum albumin species homologs).

The term “fibronectin type III (FN3) domain” (FN3 domain) as used herein refers to a domain occurring frequently in proteins including fibronectins, tenascin, intracellular cytoskeletal proteins, cytokine receptors and prokaryotic enzymes (Bork and Doolittle, Proc Nat Acad Sci USA 89:8990-8994, 1992; Meinke et al., J Bacteriol 175:1910-1918, 1993; Watanabe et al., J Biol Chem 265:15659-15665, 1990). Exemplary FN3 domains are the 15 different FN3 domains present in human tenascin C, the 15 different FN3 domains present in human fibronectin (FN), and non-natural synthetic FN3 domains as described for example in U.S. Pat. No. 8,278,419. Individual FN3 domains are referred to by domain number and protein name, e.g., the 3rd FN3 domain of tenascin (TN3), or the 10th FN3 domain of fibronectin (FN10).

“Centyrin” as used herein refers to a FN3 domain that is based on the consensus sequence of the 15 different FN3 domains present in human tenascin C.

The term “capture agent” refers to substances that bind to a particular type of cells and enable the isolation of that cell from other cells. Examples of capture agents include but are not limited to magnetic beads, ferrofluids, encapsulating reagents and the like.

The term “biological sample” refers to blood, tissue, marrow, sputum and the like.

The term “diagnostic reagent” refers to any substance that may be used to analyze a biological sample, whether or not such substance is distributed as a single substance or in a combination with other substances in a diagnostic kit.

The term “substituting” or “substituted” or ‘mutating” or “mutated” as used herein refers to altering, deleting of inserting one or more amino acids or nucleotides in a polypeptide or polynucleotide sequence to generate a variant of that sequence.

The term “randomizing” or “randomized” or “diversified” or “diversifying” as used herein refers to making at least one substitution, insertion or deletion in a polynucleotide or polypeptide sequence.

“Variant” as used herein refers to a polypeptide or a polynucleotide that differs from a reference polypeptide or a reference polynucleotide by one or more modifications for example, substitutions, insertions or deletions.

The term “specifically binds” or “specific binding” as used herein refers to the ability of the FN3 domain of the invention to bind to a predetermined antigen with a dissociation constant (K_(D)) of about 1×10⁻⁶ M or less, for example about 1×10⁻⁷M or less, about 1×10⁻⁸M or less, about 1×10⁻⁹M or less, about 1×10⁻¹⁰ M or less, about 1×10⁻¹¹ M or less, about 1×10⁻¹²M or less, or about 1×10⁻¹³ M or less. Typically the FN3 domain of the invention binds to a predetermined antigen (i.e. human CD8A) with a K_(D) that is at least ten fold less than its K_(D) for a nonspecific antigen (for example BSA or casein) as measured by surface plasmon resonance using for example a Proteon Instrument (BioRad). The isolated FN3 domain of the invention that specifically binds to human CD8A may, however, have cross-reactivity to other related antigens, for example to the same predetermined antigen from other species (orthologs), such as Macaca Fascicularis (cynomolgous monkey, cyno) or Pan troglodytes (chimpanzee).

The term “library” refers to a collection of variants. The library may be composed of polypeptide or polynucleotide variants.

As used herein, the terms “CD8A” or “CD8” specifically include the human CD8 alpha protein, for example, as described in NCBI Reference Sequence: NP_001139345.1, NP_0011759.3, and NP_741969.1. CD8A is also known in the scientific literature as CD8a molecule, MAL, p32, Leu2, T-cell surface glycoprotein CD8 alpha chain, CD8 antigen, alpha polypeptide (p32), Leu2 T-lymphocyte antigen, OKT8 T-cell antigen, T-cell antigen Leu2, T-lymphocyte differentiation antigen T8/Leu-2, and T8 T-cell antigen.

“Tencon” as used herein refers to the synthetic fibronectin type III (FN3) domain having the sequence shown in SEQ ID NO: 1 and described in U.S. Pat. Publ. No. US2010/0216708.

The term “vector” means a polynucleotide capable of being duplicated within a biological system or that can be moved between such systems. Vector polynucleotides typically contain elements, such as origins of replication, polyadenylation signal or selection markers that function to facilitate the duplication or maintenance of these polynucleotides in a biological system. Examples of such biological systems may include a cell, virus, animal, plant, and reconstituted biological systems utilizing biological components capable of duplicating a vector. The polynucleotide comprising a vector may be DNA or RNA molecules or a hybrid of these.

The term “expression vector” means a vector that can be utilized in a biological system or in a reconstituted biological system to direct the translation of a polypeptide encoded by a polynucleotide sequence present in the expression vector.

The term “polynucleotide” means a molecule comprising a chain of nucleotides covalently linked by a sugar-phosphate backbone or other equivalent covalent chemistry. Double and single-stranded DNAs and RNAs are typical examples of polynucleotides.

The term “polypeptide” or “protein” means a molecule that comprises at least two amino acid residues linked by a peptide bond to form a polypeptide. Small polypeptides of less than about 50 amino acids may be referred to as “peptides”.

The term “in combination with” as used herein means that two or more therapeutics can be administered to a subject together in a mixture, concurrently as single agents or sequentially as single agents in any order.

Compositions of Matter

The present invention provides human CD8A binding FN3 domains and CD8A binding FN3 domains conjugated to detectable labels. The present invention provides polynucleotides encoding the FN3 domains of the invention or complementary nucleic acids thereof, vectors, host cells, and methods of making and using them.

CD8A Binding Molecules

The present invention provides fibronectin type III (FN3) domains that bind specifically to CD8A, optionally conjugated to a detectable label. These molecules may be widely used in preclinical applications and in cancer diagnostics using CD8A as a biomarker. The present invention provides polynucleotides encoding the FN3 domains of the invention or complementary nucleic acids thereof, vectors, host cells, and methods of making and using them.

The FN3 domains of the invention bind CD8A with high affinity and can localize CD8-expressing cells, thereby providing an efficient way to deliver diagnostic reagents into tumor microenvironment.

One embodiment of the invention an isolated FN3 domain that specifically binds a human CD8A comprising the amino acid sequence of SEQ ID NO: 35.

In some embodiment of the invention described herein, the FN3 domain of the invention cross-reacts with cynomolgus monkey CD8A having the amino acid sequence of SEQ ID NO: 271.

The FN3 domain of the invention may bind human, Macaca Fascicularis and/or Pan troglodytes CD8A with a dissociation constant (K_(D)) of less than about 1×10⁻⁷ M, for example less than about 1×10⁻⁸ M, less than about 1×10⁻⁹ M, less than about 1×10⁻¹⁰ M, less than about 1×10⁻¹¹ M, less than about 1×10⁻¹² M, or less than about 1×10⁻¹³ M as determined by surface plasmon resonance, as practiced by those of skill in the art. The measured affinity of a particular FN3 domain-antigen interaction can vary if measured under different conditions (e.g., osmolarity, pH). Thus, measurements of affinity and other antigen-binding parameters (e.g., K_(D), K_(on), K_(off)) are made with standardized solutions of protein scaffold and antigen, and a standardized buffer, such as the buffer described herein.

In some embodiments, the CD8A binding FN3 domains comprise an initiator methionine (Met) linked to the N-terminus of the molecule.

In some embodiments, the CD8A binding FN3 domains comprise a cysteine (Cys) linked to the FN3 domain.

The addition of the N-terminal Met and/or the Cys may facilitate expression and/or conjugation of second molecules.

Another embodiment of the invention is an isolated FN3 domain that specifically binds human CD8A and wherein the CD8A-specific FN3 domain does not activate CD8+ T-cells in vitro. CD8+ T cell activation may be measured using standard methods. For example, the enzyme-linked immunospot (ELISPOT) assay may be used. The ELISPOT assay employs the sandwich enzyme-linked immunosorbent assay (ELISA) technique. The interferon-gamma antibody is pre-coated onto a PVDF (polyvinylidene difluoride)-backed microplate. Appropriately stimulated cells (cells+peptides, FN3 domains, etc) are pipetted into the wells and the microplate is placed into a humidified 37° C. CO₂ incubator for a specified period of time. During this incubation period, the immobilized interferon-gamma antibody, in the immediate vicinity of the secreting cells, binds the secreted interferon gamma. After washing away any cells and unbound substances, a second biotinylated interferon-gamma antibody is added to the wells. Following a wash to remove any unbound biotinylated antibody, alkaline-phosphatase conjugated to streptavidin is added. Unbound enzyme is subsequently removed by washing and a substrate solution (BCIP/NBT) is added. A blue-black colored precipitate forms and appears as spots at the sites of interferon-gamma localization, with each individual spot representing an individual interferon gamma-secreting cell. The spots can be counted with an automated ELISpot reader system or manually, using a stereomicroscope. The isolated CD8A binding FN3 domains of the invention do not activate CD8+ T-cells in vitro when tested at 1 μM concentrations as described in the EXAMPLES.

In some embodiments of the invention described herein, the isolated FN3 domain comprises the amino acid sequence of SEQ ID NOs: 40-269.

In some embodiments of the invention described herein, the CD8A-specific FN3 domain has a cysteine substitution at residue position 54 of SEQ ID NOs 79, 81, 83, 89, 122 and 68.

Substitutions resulting in introduction of cysteine into a protein sequence may be utilized to chemically conjugate small molecules such as cytotoxic agents, detectable labels, half-life extension molecules, chelators, polyethylene glycol and/or nucleic acids to the FN3 domain using standard chemistry.

In some embodiments, the FN3 domain specifically binding human CD8A competes for binding to human CD8A with the FN3 domain of SEQ ID NOs: 229-234. FN3 domains may be evaluated for ther competition with a reference molecule for binding human CD8A using well known in vitro methods. In an exemplary method, HEK cells recombinantly expressing human CD8A may be incubated with unlabeled reference molecule for 15 min at 4° C., followed by incubation with an excess of fluorescently labeled test FN3 domain for 45 min at 4° C. After washing in PBS/BSA, fluorescence may be measured by flow cytometry using standard methods. In another exemplary method, extracellular portion of human CD8A may be coated on the surface of an ELISA plate. Excess of unlabelled reference molecule may be added for about 15 minutes and subsequently biotinylated test FN3 domains may be added. After washes in PBS/Tween, binding of the test biotinylated FN3 domain may be detected using horseradish peroxidase (HRP)-conjugated streptavidine and the signal detected using standard methods. It is readily apparent that in the competition assays, reference molecule may be labelled and the test FN3 domain unlabeled. The test FN3 domain may compete with the reference molecule when the reference molecule inhibits binding of the test FN3 domain, or the test FN3 domain inhibits binding of the reference molecule by 20%, 30%, 40%, 50%, 60%, 70%, 80%, 85%, 90%, 95% or 100%.

In some embodiments, the isolated FN3 domain that specifically binds human CD8A of the invention is conjugated to a chelator that can bind to a radioactive metal and may be used as an imaging agent to evaluate tumor distribution, diagnosis for the presence of CD8-T cells inside tumors and/or efficacy of cancer treatment.

In some embodiments, the CD8A-specific FN3 domains are removed from the blood via renal and/or liver clearance.

Isolation of CD8A Binding FN3 Domains from a Library Based on Tencon Sequence

Tencon (SEQ ID NO: 1) is a non-naturally occurring fibronectin type III (FN3) domain designed from a consensus sequence of fifteen FN3 domains from human tenascin-C (Jacobs et al., Protein Engineering, Design, and Selection, 25:107-117, 2012; U.S. Pat. Publ. No. 2010/0216708). The crystal structure of Tencon shows six surface-exposed loops that connect seven beta-strands as is characteristic to the FN3 domains, the beta-strands referred to as A, B, C, D, E, F, and G, and the loops referred to as AB, BC, CD, DE, EF, and FG loops (Bork and Doolittle, Proc Natl Acad Sci USA 89:8990-8992, 1992; U.S. Pat. No. 6,673,901). These loops, or selected residues within each loop, may be randomized in order to construct libraries of fibronectin type III (FN3) domains that may be used to select novel molecules that bind CD8A. Table 1 shows positions and sequences of each loop and beta-strand in Tencon (SEQ ID NO: 1).

Library designed based on Tencon sequence may thus have randomized FG loop, or randomized BC and FG loops, such as libraries TCL1 or TCL2 as described below. The Tencon BC loop is 7 amino acids long, thus 1, 2, 3, 4, 5, 6 or 7 amino acids may be randomized in the library diversified at the BC loop and designed based on the Tencon sequence. The Tencon FG loop is 7 amino acids long, thus 1, 2, 3, 4, 5, 6 or 7 amino acids may be randomized in the library diversified at the FG loop and designed based on Tencon sequence. Further diversity at loops in the Tencon libraries may be achieved by insertion and/or deletions of residues at loops. For example, the FG and/or BC loops may be extended by 1-22 amino acids, or decreased by 1-3 amino acids. The FG loop in Tencon is 7 amino acids long, whereas the corresponding loop in antibody heavy chains ranges from 4-28 residues. To provide maximum diversity, the FG loop may be diversified in sequence as well as in length to correspond to the antibody CDR3 length range of 4-28 residues. For example, the FG loop can further be diversified in length by extending the loop by additional 1, 2, 3, 4 or 5 amino acids.

A library designed based on the Tencon sequence may also have randomized alternative surfaces that form on a side of the FN3 domain and comprise two or more beta strands, and at least one loop. One such alternative surface is formed by amino acids in the C and the F beta-strands and the CD and the FG loops (a C-CD-F-FG surface). A library design based on Tencon alternative C-CD-F-FG surface is is described in U.S. Pat. Publ. No. US2013/0226834. Library designed based on Tencon sequence also includes libraries designed based on Tencon variants, such as Tencon variants having substitutions at residues positions 11, 14, 17, 37, 46, 73, or 86 (residue numbering corresponding to SEQ ID NO: 1), and which variants display improve thermal stability. Exemplary Tencon variants are described in US Pat. Publ. No. 2011/0274623, and include Tencon27 (SEQ ID NO: 4) having substitutions E11R, L17A, N46V and E86I when compared to Tencon of SEQ ID NO: 1.

TABLE 1 Tencon topology Tencon FN3 domain (SEQ ID NO: 1) A strand  1-12 AB loop 13-16 B strand 17-21 BC loop 22-28 C strand 29-37 CD loop 38-43 D strand 44-50 DE loop 51-54 E strand 55-59 EF loop 60-64 F strand 65-74 FG loop 75-81 G strand 82-89

Tencon and other FN3 sequence based libraries may be randomized at chosen residue positions using a random or defined set of amino acids. For example, variants in the library having random substitutions may be generated using NNK codons, which encode all 20 naturally occurring amino acids. In other diversification schemes, DVK codons may be used to encode amino acids Ala, Trp, Tyr, Lys, Thr, Asn, Lys, Ser, Arg, Asp, Glu, Gly, and Cys. Alternatively, NNS codons may be used to give rise to all 20 amino acid residues and simultaneously reducing the frequency of stop codons. Libraries of FN3 domains with biased amino acid distribution at positions to be diversified may be synthesized for example using Slonomics® technology (http:_//www_sloning_com). This technology uses a library of pre-made double stranded triplets that act as universal building blocks sufficient for thousands of gene synthesis processes. The triplet library represents all possible sequence combinations necessary to build any desired DNA molecule. The codon designations are according to the well known IUB code.

The FN3 domains specifically binding human CD8A of the invention may be isolated by producing the FN3 library such as the Tencon library using cis display to ligate DNA fragments encoding the scaffold proteins to a DNA fragment encoding RepA to generate a pool of protein-DNA complexes formed after in vitro translation wherein each protein is stably associated with the DNA that encodes it (U.S. Pat. No. 7,842,476; Odegrip et al., Proc Natl Acad Sci USA 101, 2806-2810, 2004), and assaying the library for specific binding to CD8A by any method known in the art and described in the Example. Exemplary well known methods which can be used are ELISA, sandwich immunoassays, and competitive and non-competitive assays (see, e.g., Ausubel et al., eds, 1994, Current Protocols in Molecular Biology, Vol. 1, John Wiley & Sons, Inc., New York). The identified FN3 domains specifically binding CD8A are further characterized for their inhibition of CD8A activity, internalization, stability, and other desired characteristics.

The FN3 domains specifically binding human CD8A of the invention may be generated using any FN3 domain as a template to generate a library and screening the library for molecules specifically binding human CD8A using methods provided within. Exemplar FN3 domains that may be used are the 3rd FN3 domain of tenascin C (TN3) (SEQ ID NO: 145), Fibcon (SEQ ID NO: 146), and the 10th FN3 domain of fibronectin (FN10) (SEQ ID NO: 147). Standard cloning and expression techniques are used to clone the libraries into a vector or synthesize double stranded cDNA cassettes of the library, to express, or to translate the libraries in vitro. For example ribosome display (Hanes and Pluckthun, Proc Natl Acad Sci USA, 94, 4937-4942, 1997), mRNA display (Roberts and Szostak, Proc Natl Acad Sci USA, 94, 12297-12302, 1997), or other cell-free systems (U.S. Pat. No. 5,643,768) can be used. The libraries of the FN3 domain variants may be expressed as fusion proteins displayed on the surface for example of any suitable bacteriophage. Methods for displaying fusion polypeptides on the surface of a bacteriophage are well known (U.S. Pat. Publ. No. 2011/0118144; Int. Pat. Publ. No. WO2009/085462; U.S. Pat. Nos. 6,969,108; 6,172,197; 5,223,409; 6,582,915; 6,472,147).

In some embodiments of the invention described herein, the FN3 domain specifically binding human CD8A is based on Tencon sequence of SEQ ID NO: 1 or Tencon27 sequence of SEQ ID NO: 4, the SEQ ID NO: 1 or the SEQ ID NO: 4, optionally having substitutions at residues positions 11, 14, 17, 37, 46, 73, and/or 86.

The FN3 domains specifically binding human CD8A of the invention may be modified to improve their properties such as improve thermal stability and reversibility of thermal folding and unfolding. Several methods have been applied to increase the apparent thermal stability of proteins and enzymes, including rational design based on comparison to highly similar thermostable sequences, design of stabilizing disulfide bridges, mutations to increase alpha-helix propensity, engineering of salt bridges, alteration of the surface charge of the protein, directed evolution, and composition of consensus sequences (Lehmann and Wyss, Curr Opin Biotechnol, 12, 371-375, 2001). High thermal stability may increase the yield of the expressed protein, improve solubility or activity, decrease immunogenicity, and minimize the need of a cold chain in manufacturing. Residues that may be substituted to improve thermal stability of Tencon (SEQ ID NO: 1) are residue positions 11, 14, 17, 37, 46, 73, or 86, and are described in US Pat. Publ. No. 2011/0274623. Substitutions corresponding to these residues may be incorporated to the FN3 domain containing molecules of the invention.

Measurement of protein stability and protein lability can be viewed as the same or different aspects of protein integrity. Proteins are sensitive or “labile” to denaturation caused by heat, by ultraviolet or ionizing radiation, changes in the ambient osmolarity and pH if in liquid solution, mechanical shear force imposed by small pore-size filtration, ultraviolet radiation, ionizing radiation, such as by gamma irradiation, chemical or heat dehydration, or any other action or force that may cause protein structure disruption. The stability of the molecule can be determined using standard methods. For example, the stability of a molecule can be determined by measuring the thermal melting (“T_(m)”) temperature, the temperature in ° Celsius (° C.) at which half of the molecules become unfolded, using standard methods. Typically, the higher the T_(m), the more stable the molecule. In addition to heat, the chemical environment also changes the ability of the protein to maintain a particular three dimensional structure.

In one embodiment, the FN3 domains specifically binding human CD8A of the invention may exhibit increased stability by at least 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or 95% or more compared to the same domain prior to engineering measured by the increase in the T_(m).

Chemical denaturation can likewise be measured by a variety of methods. Chemical denaturants include guanidinium hydrochloride, guanidinium thiocyanate, urea, acetone, organic solvents (DMF, benzene, acetonitrile), salts (ammonium sulfate, lithium bromide, lithium chloride, sodium bromide, calcium chloride, sodium chloride); reducing agents (e.g. dithiothreitol, beta-mercaptoethanol, dinitrothiobenzene, and hydrides, such as sodium borohydride), non-ionic and ionic detergents, acids (e.g. hydrochloric acid (HCl), acetic acid (CH₃COOH), halogenated acetic acids), hydrophobic molecules (e.g. phosopholipids), and targeted denaturants. Quantitation of the extent of denaturation can rely on loss of a functional property, such as ability to bind a target molecule, or by physiochemical properties, such as tendency to aggregation, exposure of formerly solvent inaccessible residues, or disruption or formation of disulfide bonds.

The FN3 domains of the invention may be generated as monomers, dimers, or multimers, for example, as a means to increase the valency and thus the avidity of target molecule binding, or to generate bi- or multispecific scaffolds simultaneously binding two or more different target molecules. The dimers and multimers may be generated by linking monospecific, bi- or multispecific protein scaffolds, for example, by the inclusion of an amino acid linker, for example a linker containing poly-glycine, glycine and serine, or alanine and proline. Exemplary linker include (GS)₂, (SEQ ID NO: 148), (GGGS)₂ (SEQ ID NO: 149), (GGGGS)₅ (SEQ ID NO: 150), (AP)₂ (SEQ ID NO: 151), (AP)₅ (SEQ ID NO: 152), (AP)₁₀ (SEQ ID NO: 153), (AP)₂₀ (SEQ ID NO: 154) and A(EAAAK)₅AAA (SEQ ID NO: 142). The dimers and multimers may be linked to each other in a N- to C-direction. The use of naturally occurring as well as artificial peptide linkers to connect polypeptides into novel linked fusion polypeptides is well known in the literature (Hallewell et al., J Biol Chem 264, 5260-5268, 1989; Alfthan et al., Protein Eng. 8, 725-731, 1995; Robinson & Sauer, Biochemistry 35, 109-116, 1996; U.S. Pat. No. 5,856,456).

Diagnostic Agents

According to the invention, a CD8A-specific FN3 domain of the invention may comprise a detectable label. In an embodiment, the detectable label may be complexed with a chelating agent that is conjugated to the FN3 domain. In another embodiment, the detectable label may be complexed with a chelating agent that is conjugated to a linker that is conjugated to the FN3 domain. In still another embodiment, the detectable label may be coupled to a linker that is conjugated to the FN3 domain. In still yet another embodiment, a detectable label may be indirectly attached to a peptide of the invention by the ability of the label to be specifically bound by a second molecule. One example of this type of an indirectly attached label is a biotin label that can be specifically bound by the second molecule, streptavidin. Single, dual or multiple labeling may be advantageous. As used herein, a “detectable label” is any type of label which, when attached to an FN3 domain of the invention renders the FN3 domain detectable. A detectable label may also be toxic to cells or cytotoxic. In general, detectable labels may include luminescent molecules, chemiluminescent molecules, fluorochromes, fluorophores, fluorescent quenching agents, colored molecules, radioisotopes, radionuclides, cintillants, massive labels such as a metal atom (for detection via mass changes), biotin, avidin, streptavidin, protein A, protein G, antibodies or fragments thereof, Grb2, polyhistidine, Ni²⁺, Flag tags, myc tags, heavy metals, enzymes, alkaline phosphatase, peroxidase, luciferase, electron donors/acceptors, acridinium esters, and colorimetric substrates. In a specific embodiment, the detectable label is a radionuclide. The skilled artisan would readily recognize other useful labels that are not mentioned above, which may be employed in the operation of the present invention.

A detectable label emits a signal that can be detected by a signal transducing machine. In some cases, the detectable label can emit a signal spontaneously, such as when the detectable label is a radionuclide. In other cases, the detectable label emits a signal as a result of being stimulated by an external field such as when the detectable label is a relaxivity metal. Examples of signals include, without limitation, gamma rays, X-rays, visible light, infrared energy, and radiowaves. Examples of signal transducing machines include, without limitation, gamma cameras including SPECT/CT devices, PET scanners, fluorimeters, and Magnetic Resonance Imaging (MRI) machines. As such, the detectable label comprises a label that can be detected using magnetic resonance imaging, scintigraphic imaging, ultrasound, or fluorescence.

Suitable fluorophores include, but are not limited to, fluorescein isothiocyante (FITC), fluorescein thiosemicarbazide, rhodamine, Texas Red, CyDyes (e.g., Cy3, Cy5, Cy5.5), Alexa Fluors (e.g., Alexa488, Alexa555, Alexa594; Alexa647), near infrared (NIR) (700-900 nm) fluorescent dyes, and carbocyanine and aminostyryl dyes. An FN3 domain of the invention can be labeled for fluorescence detection by labeling the agent with a fluorophore using techniques well known in the art (see, e.g., Lohse et al., Bioconj Chem 8:503-509 (1997)). For example, many known dyes are capable of being coupled to NH₂-terminal amino acid residues. Alternatively, a fluorochrome such as fluorescein may be bound to a lysine residue of the peptide linker.

A radionuclide may be a γ-emitting radionuclide, Auger-emitting radionuclide, γ-emitting radionuclide, an alpha-emitting radionuclide, or a positron-emitting radionuclide. A radionuclide may be a detectable label and/or a cytotoxic agent. Non-limiting examples of suitable radionuclides may include carbon-11, nitrogen-13, oxygen-15, fluorine-18, fluorodeoxyglucose-18, phosphorous-32, scandium-47, copper-64, 65 and 67, gallium-67 and 68, bromine-75, 77 and 80m, rubidium-82, strontium-89, zirconium-89, yttrium-86 and 90, ruthenium-95, 97, 103 and 105, rhenium-99m, 101, 105, 186 and 188, technetium-99m, rhodium-105, mercury-107, palladium-109, indium-111, silver-111, indium-113m, lanthanide-114m, tin-117m, tellurium-121 m, 122m and 125m, iodine-122, 123, 124, 125, 126, 131 and 133, praseodymium-142, promethium-149, samarium-153, gadolinium-159, thulium-165, 167 and 168, dysprosium-165, holmium-166, lutetium-177, rhenium-186 and 188, iridium-192, platinum-193 and 195m, gold-199, thallium-201, titanium-201, astatine-21 1, bismuth-212 and 213, lead-212, radium-223, actinium-225, and nitride or oxide forms derived there from. In a specific embodiment, a radionuclide is selected from the group consisting of copper-64, zirconium-89, yttrium-90, indium-111, and lutetium-177. In another specific embodiment, a radionuclide is selected from the group consisting of yttrium-90, indium-111, and lutetium-177. In an exemplary embodiment, a radionuclide is zirconium-89.

A variety of metal atoms may be used as a detectable label. The metal atom may generally be selected from the group of metal atoms comprised of metals with an atomic number of twenty or greater. For instance, the metal atoms may be calcium atoms, scandium atoms, titanium atoms, vanadium atoms, chromium atoms, manganese atoms, iron atoms, cobalt atoms, nickel atoms, copper atoms, zinc atoms, gallium atoms, germanium atoms, arsenic atoms, selenium atoms, bromine atoms, krypton atoms, rubidium atoms, strontium atoms, yttrium atoms, zirconium atoms, niobium atoms, molybdenum atoms, technetium atoms, ruthenium atoms, rhodium atoms, palladium atoms, silver atoms, cadmium atoms, indium atoms, tin atoms, antimony atoms, tellurium atoms, iodine atoms, xenon atoms, cesium atoms, barium atoms, lanthanum atoms, hafnium atoms, tantalum atoms, tungsten atoms, rhenium atoms, osmium atoms, iridium atoms, platinum atoms, gold atoms, mercury atoms, thallium atoms, lead atoms, bismuth atoms, francium atoms, radium atoms, actinium atoms, cerium atoms, praseodymium atoms, neodymium atoms, promethium atoms, samarium atoms, europium atoms, gadolinium atoms, terbium atoms, dysprosium atoms, holmium atoms, erbium atoms, thulium atoms, ytterbium atoms, lutetium atoms, thorium atoms, protactinium atoms, uranium atoms, neptunium atoms, plutonium atoms, americium atoms, curium atoms, berkelium atoms, californium atoms, einsteinium atoms, fermium atoms, mendelevium atoms, nobelium atoms, or lawrencium atoms. In some embodiments, the metal atoms may be selected from the group comprising alkali metals with an atomic number greater than twenty. In other embodiments, the metal atoms may be selected from the group comprising alkaline earth metals with an atomic number greater than twenty. In one embodiment, the metal atoms may be selected from the group of metals comprising the lanthanides. In another embodiment, the metal atoms may be selected from the group of metals comprising the actinides. In still another embodiment, the metal atoms may be selected from the group of metals comprising the transition metals. In yet another embodiment, the metal atoms may be selected from the group of metals comprising the poor metals. In other embodiments, the metal atoms may be selected from the group comprising gold atoms, bismuth atoms, tantalum atoms, and gadolinium atoms. In preferred embodiments, the metal atoms may be selected from the group comprising metals with an atomic number of 53 (i.e. iodine) to 83 (i.e. bismuth). In an alternative embodiment, the metal atoms may be atoms suitable for magnetic resonance imaging. In another alternative embodiment, the metal atoms may be selected from the group consisting of metals that have a K-edge in the x-ray energy band of CT. Preferred metal atoms include, but are not limited to, manganese, iron, gadolinium, gold, and iodine.

The metal atoms may be metal ions in the form of +1, +2, or +3 oxidation states. For instance, non-limiting examples include Ba²⁺, Bi³⁺, Cs⁺, Ca²⁺, Cr²⁺, Cr³⁺, Cr⁶⁺, Co²⁺, Co³⁺, Cu⁺, Cu²⁺, Cu³⁺, Ga³⁺, Gd³⁺, Au⁺, Au³⁺, Fe²⁺, Fe³⁺, F³⁺, Pb²⁺, Mn²⁺, Mn³⁺, Mn⁴⁺, Mn⁷⁺, Hg²⁺, Ni²⁺, Ni³⁺, Ag⁺, Sr²⁺, Sn²⁺, Sn⁴⁺, and Zn²⁺. The metal atoms may comprise a metal oxide. For instance, non-limiting examples of metal oxides may include iron oxide, manganese oxide, or gadolinium oxide. Additional examples may include magnetite, maghemite, or a combination thereof.

According to the invention, an FN3 domain comprising a chelating agent may incorporate a radionuclide or metal atom. Incorporation of the radionuclide or metal atom with an FN3 domain-chelating agent complex may be achieved by various methods common in the art of coordination chemistry.

Half-Life Extending Moieties

The FN3 domain specifically binding human CD8A of the invention may incorporate other subunits for example via covalent interaction. In one aspect of the invention, the FN3 domain of the invention further comprises a half-life extending moiety. Exemplary half-life extending moieties are albumin, albumin variants, albumin-binding proteins and/or domains, transferrin and fragments and analogues thereof, and Fc regions.

Additional moieties may be incorporated into the FN3 domain of the invention such as polyethylene glycol (PEG) molecules, such as PEG5000 or PEG20,000, fatty acids and fatty acid esters of different chain lengths, for example laurate, myristate, stearate, arachidate, behenate, oleate, arachidonate, octanedioic acid, tetradecanedioic acid, octadecanedioic acid, docosanedioic acid, and the like, polylysine, octane, carbohydrates (dextran, cellulose, oligo- or polysaccharides) for desired properties. These moieties may be direct fusions with the protein scaffold coding sequences and may be generated by standard cloning and expression techniques. Alternatively, well known chemical coupling methods may be used to attach the moieties to recombinantly produced molecules of the invention.

A pegyl moiety may for example be added to the FN3 domain of the invention by incorporating a cysteine residue to the C-terminus of the molecule, or engineering cysteines into residue positions that face away from the human CD8A binding face of the molecule, and attaching a pegyl group to the cysteine using well known methods. FN3 domain of the invention incorporating additional moieties may be compared for functionality by several well known assays. For example, altered properties due to incorporation of Fc domains and/or Fc domain variants may be assayed in Fc receptor binding assays using soluble forms of the receptors, such as the FcγRI, FcγRII, FcγRIII or FcRn receptors, or using well known cell-based assays measuring for example ADCC or CDC, or evaluating pharmacokinetic properties of the molecules of the invention in in vivo models.

Polynucleotides, Vectors, Host Cells

The invention provides for nucleic acids encoding the FN3 domains specifically binding human CD8A of the invention as isolated polynucleotides or as portions of expression vectors or as portions of linear DNA sequences, including linear DNA sequences used for in vitro transcription/translation, vectors compatible with prokaryotic, eukaryotic or filamentous phage expression, secretion and/or display of the compositions or directed mutagens thereof. Certain exemplary polynucleotides are disclosed herein, however, other polynucleotides which, given the degeneracy of the genetic code or codon preferences in a given expression system, encode the FN3 domains of the invention are also within the scope of the invention.

One embodiment of the invention is an isolated polynucleotide encoding the FN3 domain specifically binding human CD8A comprising the amino acid sequence of SEQ ID NOs: 40-269.

The polynucleotides of the invention may be produced by chemical synthesis such as solid phase polynucleotide synthesis on an automated polynucleotide synthesizer and assembled into complete single or double stranded molecules. Alternatively, the polynucleotides of the invention may be produced by other techniques such a PCR followed by routine cloning. Techniques for producing or obtaining polynucleotides of a given known sequence are well known in the art.

The polynucleotides of the invention may comprise at least one non-coding sequence, such as a promoter or enhancer sequence, intron, polyadenylation signal, a cis sequence facilitating RepA binding, and the like. The polynucleotide sequences may also comprise additional sequences encoding additional amino acids that encode for example a marker or a tag sequence such as a histidine tag or an HA tag to facilitate purification or detection of the protein, a signal sequence, a fusion protein partner such as RepA, Fc or bacteriophage coat protein such as pIX or pIII.

Another embodiment of the invention is a vector comprising at least one polynucleotide of the invention. Such vectors may be plasmid vectors, viral vectors, vectors for baculovirus expression, transposon based vectors or any other vector suitable for introduction of the polynucleotides of the invention into a given organism or genetic background by any means. Such vectors may be expression vectors comprising nucleic acid sequence elements that can control, regulate, cause or permit expression of a polypeptide encoded by such a vector. Such elements may comprise transcriptional enhancer binding sites, RNA polymerase initiation sites, ribosome binding sites, and other sites that facilitate the expression of encoded polypeptides in a given expression system. Such expression systems may be cell-based, or cell-free systems well known in the art.

Another embodiment of the invention is a host cell comprising the vector of the invention. The FN3 domain specifically binding human CD8A of the invention may be optionally produced by a cell line, a mixed cell line, an immortalized cell or clonal population of immortalized cells, as well known in the art. See, e.g., Ausubel, et al., ed., Current Protocols in Molecular Biology, John Wiley & Sons, Inc., NY, NY (1987-2001); Sambrook, et al., Molecular Cloning: A Laboratory Manual, 2nd Edition, Cold Spring Harbor, N.Y. (1989); Harlow and Lane, Antibodies, a Laboratory Manual, Cold Spring Harbor, N.Y. (1989); Colligan, et al., eds., Current Protocols in Immunology, John Wiley & Sons, Inc., NY (1994-2001); Colligan et al., Current Protocols in Protein Science, John Wiley & Sons, NY, NY, (1997-2001).

The host cell chosen for expression may be of mammalian origin or may be selected from COS-1, COS-7, HEK293, BHK21, CHO, BSC-1, He G2, SP2/0, HeLa, myeloma, lymphoma, yeast, insect or plant cells, or any derivative, immortalized or transformed cell thereof. Alternatively, the host cell may be selected from a species or organism incapable of glycosylating polypeptides, e.g. a prokaryotic cell or organism, such as BL21, BL21(DE3), BL21-GOLD(DE3), XL1-Blue, JM109, HMS174, HMS174 (DE3), and any of the natural or engineered E. coli spp, Klebsiella spp., or Pseudomonas spp strains.

Another embodiment of the invention is a method of producing the isolated FN3 domain specifically binding human CD8A of the invention, comprising culturing the isolated host cell of the invention under conditions such that the isolated FN3 domain specifically binding human CD8A is expressed, and purifying the FN3 domain.

The FN3 domain specifically binding human CD8A may be purified from recombinant cell cultures by well-known methods, for example by protein A purification, ammonium sulfate or ethanol precipitation, acid extraction, anion or cation exchange chromatography, phosphocellulose chromatography, hydrophobic interaction chromatography, affinity chromatography, hydroxylapatite chromatography and lectin chromatography, or high performance liquid chromatography (HPLC).

Kits for Detecting Human CD8A

Provided herein are kits for detecting CD8A in a biological sample. These kits include one or more of the CD8A-specific FN3 domains described herein and instructions for use of the kit.

The provided CD8A-specific FN3 domain may be in solution; lyophilized; affixed to a substrate, carrier, or plate; or detectably labeled.

The described kits may also include additional components useful for performing the methods described herein. By way of example, the kits may comprise means for obtaining a sample from a subject, a control or reference sample, e.g., a sample from a subject having slowly progressing cancer and/or a subject not having cancer, one or more sample compartments, and/or instructional material which describes performance of a method of the invention and tissue specific controls or standards.

The means for determining the level of CD8A can further include, for example, buffers or other reagents for use in an assay for determining the level of CD8A. The instructions can be, for example, printed instructions for performing the assay and/or instructions for evaluating the level of CD8A.

The described kits may also include means for isolating a sample from a subject. These means can comprise one or more items of equipment or reagents that can be used to obtain a fluid or tissue from a subject. The means for obtaining a sample from a subject may also comprise means for isolating blood components, such as serum, from a blood sample. Preferably, the kit is designed for use with a human subject.

Uses of Human CD8A Binding FN3 Domains of the Invention

The FN3 domains specifically binding human CD8A of the invention may be used to diagnose human disease or specific pathologies in cells, tissues, organs, fluid, or, generally, a host, using CD8A as a biomarker. The methods of the invention may be used in an animal patient belonging to any classification. Examples of such animals include mammals such as humans, rodents, dogs, cats and farm animals.

EXAMPLES

The following examples are provided to supplement the prior disclosure and to provide a better understanding of the subject matter described herein. These examples should not be considered to limit the described subject matter. It is understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or changes in light thereof will be apparent to persons skilled in the art and are to be included within, and can be made without departing from, the true scope of the invention.

Example 1. Construction of Tencon Libraries with Randomized Loops

Tencon (SEQ ID NO: 1) is an immunoglobulin-like scaffold, fibronectin type III (FN3) domain, designed from a consensus sequence of fifteen FN3 domains from human tenascin-C (Jacobs et al., Protein Engineering, Design, and Selection, 25:107-117, 2012; U.S. Pat. No. 8,278,419). The crystal structure of Tencon shows six surface-exposed loops that connect seven beta-strands. These loops, or selected residues within each loop, can be randomized in order to construct libraries of fibronectin type III (FN3) domains that can be used to select novel molecules that bind to specific targets. Tencon:

LPAPKNLVVSEVTEDSLRLSWTAPDAAFDSFLIQYQESEKVG EAINLTVPGSERSYDLTGLKPGTEYTVSIYGVKGGHRSNPLS AEFTT (SEQ ID NO 1): Various libraries were generated using the tencon scaffold and various design strategies. In general, libraries TCL1 and TCL2 produced good binders. Generation of TCL1 and TCL2 libraries are described in detail in Int. Pat. Publ. No. WO2014081944A2.

Construction of TCL1 Library

A library designed to randomize only the FG loop of Tencon (SEQ ID NO: 1), TCL1, was constructed for use with the cis-display system (Jacobs et al., Protein Engineering, Design, and Selection, 25:107-117, 2012). In this system, a double-stranded DNA incorporating sequences for a Tac promoter, Tencon library coding sequence, RepA coding sequence, cis-element, and ori element is produced. Upon expression in an in vitro transcription/translation system, a complex is produced of the Tencon-RepA fusion protein bound in cis to the DNA from which it is encoded. Complexes that bind to a target molecule are then isolated and amplified by polymerase chain reaction (PCR), as described below.

Construction of the TCL1 library for use with cis-display was achieved by successive rounds of PCR to produce the final linear, double-stranded DNA molecules in two halves; the 5′ fragment contains the promoter and Tencon sequences, while the 3′ fragment contains the repA gene and the cis- and ori elements. These two halves are combined by restriction digest in order to produce the entire construct. The TCL1 library was designed to incorporate random amino acids only in the FG loop of Tencon, KGGHRSN (SEQ ID NO: 32). NNS codons were used in the construction of this library, resulting in the possible incorporation of all 20 amino acids and one stop codon into the FG loop. The TCL1 library contains six separate sub-libraries, each having a different randomized FG loop length, from 7 to 12 residues, in order to further increase diversity.

TCL1 library (SEQ ID NO: 2) LPAPKNLVVSEVTEDSLRLSWTAPDAAFDSFLIQYQESEKVG EAINLTVPGSERSYDLTGLKPGTEYTVSIYGVX₇₋₁₂PLSAE FTT; wherein X₁, X₂, X₃, X₄, X₅, X₆, X₇ is any amino acid; and X₈, X₉, X₁₀, X₁₁ and X₁₂ are any amino acid or deleted

Construction of TCL2 Library

TCL2 library was constructed in which both the BC and the FG loops of Tencon were randomized and the distribution of amino acids at each position was strictly controlled. Table 2 shows the amino acid distribution at desired loop positions in the TCL2 library. The designed amino acid distribution had two aims. First, the library was biased toward residues that were predicted to be structurally important for Tencon folding and stability based on analysis of the Tencon crystal structure and/or from homology modeling. For example, position 29 was fixed to be only a subset of hydrophobic amino acids, as this residue was buried in the hydrophobic core of the Tencon fold. A second layer of design included biasing the amino acid distribution toward that of residues preferentially found in the heavy chain HCDR3 of antibodies, to efficiently produce high-affinity binders (Birtalan et al., J Mol Biol 377:1518-28, 2008; Olson et al., Protein Sci 16:476-84, 2007). Towards this goal, the “designed distribution” in Table 1 refers to the distribution as follows: 6% alanine, 6% arginine, 3.9% asparagine, 7.5% aspartic acid, 2.5% glutamic acid, 1.5% glutamine, 15% glycine, 2.3% histidine, 2.5% isoleucine, 5% leucine, 1.5% lysine, 2.5% phenylalanine, 4% proline, 10% serine, 4.5% threonine, 4% tryptophan, 17.3% tyrosine, and 4% valine. This distribution is devoid of methionine, cysteine, and STOP codons.

TCL2 library (SEQ ID NO: 3) LPAPKNLVVSEVTEDSLRLSWX₁X₂X₃X₄X₅X₆X₇X₈SFLIQYQ ESEKVGEAINLTVPGSERSYDLTGLKPGTEYTVSIYGVX₉X₁₀ X₁₁X₁₂X₁₃SX₁₄X₁₅LSAEFTT; wherein X₁ is Ala, Arg, Asn, Asp, Glu, Gln, Gly, His, Ile, Leu, Lys, Phe, Pro, Ser, Thr, Trp, Tyr or Val; X₂ is Ala, Arg, Asn, Asp, Glu, Gln, Gly, His, Ile, Leu, Lys, Phe, Pro, Ser, Thr, Trp, Tyr or Val; X₃ Ala, Arg, Asn, Asp, Glu, Gln, Gly, His, Ile, Leu, Lys, Phe, Pro, Ser, Thr, Trp, Tyr or Val; X₄ is Ala, Arg, Asn, Asp, Glu, Gln, Gly, His, Ile, Leu, Lys, Phe, Pro, Ser, Thr, Trp, Tyr or Val; X₅ is Ala, Arg, Asn, Asp, Glu, Gln, Gly, His, Ile, Leu, Lys, Phe, Pro, Ser, Thr, Trp, Tyr or Val; X₆ is Ala, Arg, Asn, Asp, Glu, Gln, Gly, His, Ile, Leu, Lys, Phe, Pro, Ser, Thr, Trp, Tyr or Val; X₇ is Phe, Ile, Leu, Val or Tyr; X₈ is Asp, Glu or Thr; X₉ is Ala, Arg, Asn, Asp, Glu, Gln, Gly, His, Ile, Leu, Lys, Phe, Pro, Ser, Thr, Trp, Tyr or Val; X₁₀ is Ala, Arg, Asn, Asp, Glu, Gln, Gly, His, Ile, Leu, Lys, Phe, Pro, Ser, Thr, Trp, Tyr or Val; X₁₁ is Ala, Arg, Asn, Asp, Glu, Gln, Gly, His, Ile, Leu, Lys, Phe, Pro, Ser, Thr, Trp, Tyr or Val; X₁₂ is Ala, Arg, Asn, Asp, Glu, Gln, Gly, His, He, Leu, Lys, Phe, Pro, Ser, Thr, Trp, Tyr or Val; X₁₃ is Ala, Arg, Asn, Asp, Glu, Gln, Gly, His, He, Leu, Lys, Phe, Pro, Ser, Thr, Trp, Tyr or Val; X₁₄ is Ala, Arg, Asn, Asp, Glu, Gln, Gly, His, Ile, Leu, Lys, Phe, Pro, Ser, Thr, Trp, Tyr or Val; and X₁₅ is Ala, Arg, Asn, Asp, Glu, Gln, Gly, His, Ile, Leu, Lys, Phe, Pro, Ser, Thr, Trp, Tyr or Val.

TABLE 1 Residue Position* WT residues Distribution in the TCL2 library 22 T designed distribution 23 A designed distribution 24 P 50% P + designed distribution 25 D designed distribution 26 A 20% A + 20% G + designed distribution 27 A designed distribution 28 F 20% F, 20% I, 20% L, 20% V, 20% Y 29 D 33% D, 33% E, 33% T 75 K designed distribution 76 G designed distribution 77 G designed distribution 78 H designed distribution 79 R designed distribution 80 S 100% S 81 N designed distribution 82 P 50% P + designed distribution *residue numbering is based on Tencon sequence of SEQ ID NO: 1

Subsequently, these libraries were improved by various ways, including building of the libraries on a stabilized Tencon framework (U.S. Pat. No. 8,569,227) that incorporates substitutions E11R/L17A/N46V/E86I (Tencon27; SEQ ID NO: 4) when compared to the wild type tencon as well as altering of the positions randomized in the BC and FG loops. Tencon27 is described in Int. Pat. Appl. No. WO2013049275. From this, new libraries designed to randomize only the FG loop of Tencon (library TCL9), or a combination of the BC and FG loops (library TCL7) were generated. These libraries were constructed for use with the cis-display system (Odegrip et al., Proc Natl Acad Sci USA 101: 2806-2810, 2004). The details of this design are shown below:

Stabilized Tencon (Tencon27) (SEQ ID NO: 4) LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFLIQYQESEKVGEAIVLTVP GSERSYDLTGLKPGTEYTVSIYGVKGGHRSNPLSAIFTT TCL7 (randomized FG and BC loops) (SEQ ID NO: 5) LPAPKNLVVSRVTEDSARLSWX₁X₂X₃X₄X₅X₆X₇X₈X₉FDSFLIQYQES EKVGEAIVLTVPGSERSYDLTGLKPGTEYTVSIYGVX₁₀X₁₁X₁₂X₁₃ X₁₄X₁₅X₁₆X₁₇X₁₈X₁₉SNPLSAIFTT; wherein X₁, X₂, X₃, X₄, X₅, X₆, X₁₀, X₁₁, X₁₂, X₁₃, X₁₄, X₁₅ and X₁₆ is A, D, E, F, G, H, I, K, L, N, P, Q, R, S, T, V, W or Y; and X₇, X₈, X₉, X₁₇, X₁₈ and X₁₉, is A, D, E, F, G, H, I, K, L, N, P, Q, R, S, T, V, W, Y or deleted.

TCL9 (randomized FG loop) (SEQ ID NO: 6) LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFLIQYQESEKVGEAIVLTVP GSERSYDLTGLKPGTEYTVSIYGVX₁X₂X₃X₄X₅X₆X₇X₈X₉X₁₀X₁₁ X₁₂SNPLSAIFTT; X₁, X₂, X₃, X₄, X₅, X₆ and X₇, is A, D, E, F, G, H, I, K, L, N, P, Q, R, S, T, V, W or Y; and X₈, X₉, X₁₀, X₁₁ and X₁₂ is A, D, E, F, G, H, I, K, L, N, P, Q, R, S, T, V, W, Y or deleted.

For library construction, DNA fragments encoding randomized BC loops (lengths 6-9 positions) or FG loops (lengths 7-12 positions) were synthesized using Slonomics technology (Sloning Biotechnology GmbH) so as to control the amino acid distribution of the library and to eliminate stop codons. Two different sets of DNA molecules randomizing either the BC loop or the FG loops were synthesized independently and later combined using PCR to produce the full library product.

Construction of FG Loop Libraries (TCL9)

A set of synthetic DNA molecules consisting of a 5′ Tac promoter followed by the complete gene sequence of Tencon with the exception of randomized codons in the FG loop was produced (SEQ ID NOs: 26-31). For FG loop randomization, all amino acids except cysteine and methionine were encoded at equal percentages. The lengths of the diversified portion are such that they encode for 7, 8, 9, 10, 11, or 12 amino acids in the FG loop. Sub-libraries of each length variation were synthesized individually at a scale of 2 ug and then amplified by PCR using oligos Sloning-FOR (SEQ ID NO: 9) and Sloning-Rev (SEQ ID NO: 10).

The 3′ fragment of the library is a constant DNA sequence containing elements for display, including a PspOMI restriction site, the coding region of the repA gene, and the cis- and ori elements. PCR reactions were performed to amplify this fragment using a plasmid (pCR4Blunt) (Invitrogen) as a template with M13 Forward and M13 Reverse primers. The resulting PCR products were digested by PspOMI overnight and gel-purified. To ligate the 5′ portion of library DNA to the 3′ DNA containing repA gene, 2 pmol (˜540 ng to 560 ng) of 5′ DNA was ligated to an equal molar (˜1.25 μg) of 3′ repA DNA in the presence of NotI and PspOMI enzyme and T4 ligase at 37° C. overnight. The ligated library product was amplified by using 12 cycles of PCR with oligos POP2250 (SEQ ID NO: 11) and DigLigRev (SEQ ID NO: 12). For each sub-library, the resulting DNA from 12 PCR reactions were combined and purified by Qiagen spin column. The yield for each sub-library of TCL9 ranged from 32-34 μg.

Construction of FG/BC Loop Libraries (TCL7)

The TCL7 library provides for a library with randomized Tencon BC and FG loops. In this library, BC loops of lengths 6-9 amino acids were mixed combinatorially with randomized FG loops of 7-12 amino acids in length. Synthetic Tencon fragments BC6, BC7, BC8, and BC9 (SEQ ID No. 13-16) were produced to include the Tencon gene encoding for the N-terminal portion of the protein up to and including residue VX such that the BC loop is replaced with either 6, 7, 8, or 9 randomized amino acids. These fragments were synthesized prior to the discovery of L17A, N46V and E831 mutations (CEN5243) but these mutations were introduced in the molecular biology steps described below. In order to combine this fragment with fragments encoding for randomized FG loops, the following steps were taken.

First, a DNA fragment encoding the Tac promoter and the 5′ sequence of Tencon up to the nucleotide endoding for amino acid A17 (130mer-L17A, SEQ ID No. 17) was produced by PCR using oligos POP2222ext (SEQ ID No. 18) and LS1114 (SEQ ID No. 19). This was done to include the L17A mutation in the library (CEN5243). Next, DNA fragments encoding for Tencon residues R18-V75 including randomized BC loops were amplified by PCR using BC6, BC7, BC8, or BC9 as a templates and oligos LS1115 (SEQ ID No. 20) and LS1117 (SEQ ID No. 21). This PCR step introduced a BsaI site at the 3′ end. These DNA fragments were subsequently joined by overlapping PCR using oligos POP2222ext and LS1117 as primers. The resulting PCR product of 240 bp was pooled and purified by Qiagen PCR purification kit. The purified DNA was digested with BsaI-HF and gel purified.

Fragments encoding the FG loop were amplified by PCR using FG7 (SEQ ID No. 31), FG8 (SEQ ID No. 30), FG9 (SEQ ID No. 29), FG10 (SEQ ID No. 28), FG11 (SEQ ID No. 27), and FG12 (SEQ ID No. 26) as templates with oligonucleotides SDG10 (SEQ ID No. 22) and SDG24 (SEQ ID No. 23) to incorporate a BsaI restriction site and N46V and E86I variations (CEN5243).

The digested BC fragments and FG fragments were ligated together in a single step using a 3-way ligation. Four ligation reactions in the 16 possible combinations were set up, with each ligation reaction combining two BC loop lengths with 2 FG loop lengths. Each ligation contained ˜300 ng of total BC fragment and 300 ng of the FG fragment. These 4 ligation pools were then amplified by PCR using oligos POP2222 (SEQ ID No. 24) and SDG28 (SEQ ID No. 25). 7.5 μg of each reaction product were then digested with NotI and cleaned up with a Qiagen PCR purification column. 5.2 μg of this DNA, was ligated to an equal molar amount of RepA DNA fragment (˜14 μg) digested with PspOMI and the product amplified by PCR using oligos POP2222.

Example 2: Generation of Tencon Libraries Having Alternative Binding Surfaces

The choice of residues to be randomized in a particular library design governs the overall shape of the interaction surface created. X-ray crystallographic analysis of an FN3 domain containing scaffold protein selected to bind maltose binding protein (MBP) from a library in which the BC, DE, and FG loops were randomized was shown to have a largely curved interface that fits into the active site of MBP (Koide et al., Proc Natl Acad Sci USA 104: 6632-6637, 2007). In contrast, an ankyrin repeat scaffold protein that was selected to bind to MBP was found to have a much more planar interaction surface and to bind to the outer surface of MBP distant from the active (Binz et al., Nat Biotechnol 22: 575-582, 2004). These results suggest that the shape of the binding surface of a scaffold molecule (curved vs. flat) may dictate what target proteins or specific epitopes on those target proteins are able to be bound effectively by the scaffold. Published efforts around engineering protein scaffolds containing FN3 domains for protein binding has relied on engineering adjacent loops for target binding, thus producing curved binding surfaces. This approach may limit the number of targets and epitopes accessible by such scaffolds.

Tencon and other FN3 domains contain two sets of CDR-like loops lying on the opposite faces of the molecule, the first set formed by the BC, DE, and FG loops, and the second set formed by the AB, CD, and EF loops. The two sets of loops are separated by the beta-strands that form the center of the FN3 structure. If the image of the Tencon is rotated by 90 degrees, an alternative surface can be visualized. This slightly concave surface is formed by the CD and FG loops and two antiparallel beta-strands, the C and the F beta-strands, and is herein called the C-CD-F-FG surface. The C-CD-F-FG surface can be used as a template to design libraries of protein scaffold interaction surfaces by randomizing a subset of residues that form the surface. Beta-strands have a repeating structure with the side chain of every other residue exposed to the surface of the protein. Thus, a library can be made by randomizing some or all surface exposed residues in the beta strands. By choosing the appropriate residues in the beta-strands, the inherent stability of the Tencon scaffold should be minimally compromised while providing a unique scaffold surface for interaction with other proteins.

Library TCL14 (SEQ ID NO: 7), was designed into Tencon27 scaffold (SEQ ID NO: 4).

A full description of the methods used to construct this library is described in US. Pat. Publ. No. 2013/0226834.

TCL14 library (SEQ ID NO: 7): LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFX₁IX₂YX₃EX₄X₅X₆X₇GE AIVLTVPGSERSYDLTGLKPGTEYX₈VX₉IX₁₀GVKGGX₁₁X₁₂SX₁₃PL SAIFTT;

Wherein

X₁, X₂, X₃, X₄, X₅, X₆, X₁₀, X₁₁, X₁₂ and X₁₃ are A, D, E, F, G, H, I, K, L, N, P, Q, R, S, T, V, W, Y, or M.

The two beta strands forming the C-CD-F-FG surface in Tencon27 have a total of 9 surface exposed residues that could be randomized; C-strand: S30, L32, Q34, Q36; F-strand: E66, T68, S70, Y72, and V74, while the CD loop has 6 potential residues: S38, E39, K40, V41, G42, and E43 and the FG loop has 7 potential residues: K75, G76, G77, H78, R79, S80, and N81. Select residues were chosen for inclusion in the TCL14 design due to the larger theoretical size of the library if all 22 residues were randomized.

Thirteen positions in Tencon were chosen for randomizing: L32, Q34 and Q36 in C-strand, S38, E39, K40 and V41 in CD-loop, T68, S70 and Y72 in F-strand, H78, R79, and N81 in FG-loop. In the C and F strands S30 and E66 were not randomized as they lie just beyond the CD and FG loops and do not appear to be as apparently a part of the C-CD-F-FG surface. For the CD loop, G42 and E43 were not randomized as glycine, providing flexibility, can be valuable in loop regions, and E43 lies at the junction of the surface. The FG loop had K75, G76, G77, and S80 excluded. The glycines were excluded for the reasons above while careful inspection of the crystal structures revealed S80 making key contacts with the core to help form the stable FG loop. K75 faces away from the surface of the C-CD-F-FG surface and was a less appealing candidate for randomization. Although the above mentioned residues were not randomized in the original TCL14 design, they could be included in subsequent library designs to provide additional diversity for de novo selection or for example for an affinity maturation library on a select TCL14 target specific hit.

Subsequent to the production of TCL14, 3 additional Tencon libraries of similar design were produced. These two libraries, TCL19, TCL21 and TCL23, are randomized at the same positions as TCL14 (see above) however the distribution of amino acids occurring at these positions is altered (Table 2). TCL19 and TCL21 were designed to include an equal distribution of 18 natural amino acids at every position (5.55% of each), excluding only cysteine and methionine. TCL23 was designed such that each randomized position approximates the amino acid distribution found in the HCDR3 loops of functional antibodies (Birtalan et al., J Mol Biol 377: 1518-1528, 2008) as described in Table 2. As with the TCL21 library, cysteine and methionine were excluded.

A third additional library was built to expand potential target binding surface of the other libraries library. In this library, TCL24, 4 additional Tencon positions were randomized as compared to libraries TCL14, TCL19, TCL21, and TCL23. These positions include N46 and T48 from the D strand and S84 and 186 from the G strand. Positions 46, 48, 84, and 86 were chosen in particular as the side chains of these residues are surface exposed from beta-strands D and G and lie structurally adjacent to the randomized portions of the C and F strand, thus increasing the surface area accessible for binding to target proteins. The amino acid distribution used at each position for TCL24 is identical to that described for TCL19 and TCL21 in Table 2.

TCL24 Library (SEQ ID NO: 8) LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFX₁IX₂YX₃EX₄X₅X₆X₇GE AIX₈LX₉VPGSERSYDLTGLKPGTEYX₁₀VX₁₁IX₁₂GVKGGX₁₃X₁₄S X₁₅PLX₁₆AX₁₇FTT; wherein X₁, X₂, X₃, X₄, X₅, X₆, X₁₀, X₁₁, X₁₂ and X₁₃ are A, D, E, F, G, H, I, K, L, N, P, Q, R, S, T, V or W.

TABLE 2 Amino acid frequency (%) at each randomized position for TCL21, TCL23, and TCL24. Amino Acid TCL19 TCL21 TCL23 TCL24 Ala 5.6 5.6 6.0 5.6 Arg 5.6 5.6 6.0 5.6 Asn 5.6 5.6 3.9 5.6 Asp 5.6 5.6 7.5 5.6 Cys 0.0 0.0 0.0 0.0 Gln 5.6 5.6 1.5 5.6 Glu 5.6 5.6 2.5 5.6 Gly 5.6 5.6 15.0 5.6 His 5.6 5.6 2.3 5.6 Ile 5.6 5.6 2.5 5.6 Leu 5.6 5.6 5.0 5.6 Lys 5.6 5.6 1.5 5.6 Met 0.0 0.0 0.0 0.0 Phe 5.6 5.6 2.5 5.6 Pro 5.6 5.6 4.0 5.6 Ser 5.6 5.6 10.0 5.6 Thr 5.6 5.6 4.5 5.6 Trp 5.6 5.6 4.0 5.6 Tyr 5.6 5.6 17.3 5.6 Val 5.6 5.6 4.0 5.6

Generation of TCL21, TCL23, and TCL24 Libraries

The TCL21 library was generated using Colibra library technology (Isogenica) in order to control amino acid distributions. TCL19, TCL23, and TCL24 gene fragments were generated using Slonomics technology (Morphosys) to control amino acid distributions. PCR was used to amplify each library following initial synthesis followed by ligation to the gene for RepA in order to be used in selections using the CIS-display system (Odegrip et al., Proc Natl Acad Sci USA 101: 2806-2810, 2004) as described above for the loop libraries.

Example 3: Selection of Fibronectin Type III (FN3) Domains that Bind Cd8A Design and Production of Human CD8 Alpha Antigens:

Two human CD8 alpha (Swiss Prot P01732) constructs were expressed and purified from HEK cells to produce recombinant protein for CIS-Display panning (Table 3).

TABLE 3 CD8A constructs generated for use as antigens Construct SEQID No. Description CD8W7 35 Human CD8 alpha residues 22-167 fused to Fc fragment of human IgG1 CD8W13 36 Human CD8 alpha residues 22-182 fused to Fc fragment of human IgG1 Each construct was designed to include a murine IgG Kappa secretion signal (SEQ ID No 3) and was fused to the Fc fragment of human IgG1 (SEQID No. 4). The CD8 alpha and Fc fragment sequences were connected by a linker containing a flag and polyhistidine tag sequence (SEQID No 5.)

Plasmids encoding these proteins were transfected into HEK 293-Expi cells by transient transfection and culture supernatants were harvested by centrifugation at 6000×g and clarified with a 0.2 micron filter. Supernatants were loaded onto a HiTrap Mabsure Select column (GE Healthcare) and CD8A proteins eluted in 0.1 M Na-Acetate pH 3.5 and neutralized by addition of 2M Tris pH 7. Each sample was then dialyzed into PBS pH 7.4 for biotinylation with a No Weigh EZ-Link-Sulfo-NHS-LC-Biotin biotinylation kit (Thermo Scientific).

Library Screening

Cis-display was used to select human CD8 alpha-binding domains from the TCL18, TCL19, TCL21, TCL23, and TCL24 libraries. Biotinylated CD8W7 and CD8W13 were used for panning. For in vitro transcription and translation (ITT), 3 μg of library DNA were incubated with 0.1 mM complete amino acids, 1×S30 premix components, and 15 μL of S30 extract (Promega) in a total volume of 50 μL and incubated at 30° C. After 1 hour, 375 μL of blocking solution ((0.1% Casein (Thermo Fisher, Rockford, Ill.), 100 mg/ml Herring Sperm DNA (Promega, Madison, Wis.), 1 mg/mL heparin (Sigma-Aldrich, St. Louis, Mo.)) was added and the reaction was incubated on ice for 15 minutes. For selection, biotinylated antigen was added at concentrations of 400 nM (Round 1), 200 nM (Rounds 2 and 3) and 100 nM (Rounds 4 and 5). Bound library members were recovered using neutravidin magnetic beads (Thermo Fisher, Rockford, Ill.) (Rounds 1, 3, and 5) or streptavidin magnetic beads (Promega, Madison, Wis.) (Rounds 2 and 4) and unbound library members were removed by washing the beads 5-14 times with 500 μL PBST followed by 2 washes with 500 μL PBS. Additional selection rounds were performed in order to identify scaffold molecules with improved affinities. Briefly, outputs from round 5 were prepared as described above and subjected to additional iterative rounds of selection with the following changes: the biotinylated target concentration decreased to 25 nM (Rounds 6 and 7) or 2.5 nM (Rounds 8 and 9), and an additional 1 hour wash was performed in the presence of an excess of non-biotinylated target protein. The goal of these changes was to simultaneously select for binders with a potentially faster on-rate and a slower off-rate yielding a substantially lower K_(D).

Following panning, selected FN3 domains were amplified by PCR using oligos Tcon6 (SEQID NO: 33) and Tcon5shortE86I (SEQID NO: 34), subcloned by annealing into a pET15-LIC and transformed into BL21-GOLD (DE3) cells (Agilent, Santa Clara, Calif.) for soluble expression in E. coli using standard molecular biology techniques. Single clones were picked and grown to saturation in 1 mL LB with ampicillin in 96 deepwell plates at 37° C. The following day, 25 uL was transferred to fresh 1 mL LB-Amp media in 96 deepwell plates and grown at 37° C. for 2 hours. IPTG was added at 1 mM final concentration and protein expression was induced at 30° C. for 16 hours. The cells were harvested by centrifugation and subsequently lysed with Bugbuster HT (EMD Chemicals, Gibbstown, N.J.) supplemented with 0.2 mg/mL final Chicken Egg White Lysozyme (Sigma-Aldrich, St. Louis, Mo.). Cells were harvested approximately 16 hours later by centrifugation and frozen at −20° C. Cell lysis was achieved by incubating each pellet in 0.6 mL of BugBuster® HT lysis buffer (Novagen EMD Biosciences) with shaking at room temperature for 45 minutes.

Selection of FN3 Domains that Bind CD8A

Neutravidin-coated plates were blocked for 1 hour in Starting Block T20 (Pierce) and then coated with biotinylated CD8W7 or CD8W13 (same antigen as in panning) or negative control (human Fc) for 1 hour. Plates were rinsed with TBST and diluted lysate was applied to plates for 1 hour. Following additional rinses, wells were treated with HRP-conjugated anti-FN3 domain antibody (PAB25) for 1 h and then assayed with POD (Roche). FN3 domain molecules with signals at least 10-fold above background were selected for further analysis.

Small Scale Expression and Purification of Identified FN3 Domains Binding CD8A

Isolated clones from unique hits identified by biochemical binding ELISA were combined into a single hit plate for growth in 96-well block plates; clones grew in 1 mL cultures (LB media supplemented with kanamycin for selection) at 37° C. overnight with shaking. For protein expression in 96-block plates, 1 mL TB media supplemented with kanamycin was inoculated with 50 uL of the overnight culture and grown at 37° C. with continual shaking at 300 rpm until OD₆₀₀=0.6-1. Once the target OD was reached, protein expression was induced with addition of IPTG to 1 mM; plates were transferred to 30° C. (300 rpm) for overnight growth. Overnight cultures were centrifuged to harvest the cells; bacterial pellets were stored at −80° C. until ready for use. Pellets were lysed with BugBuster® HT lysis buffer (Novagen EMD Biosciences) and His-tagged Centyrins purified from the clarified lysates with His MultiTrap™ HP plates (GE Healthcare) and eluted in buffer containing 20 mM sodium phosphate, 500 mM sodium chloride, and 250 mM imidazole at pH 7.4. Purified samples were exchanged into PBS pH 7.4 for analysis using PD MultiTrap™ G-25 plates (GE Healthcare).

Size Exclusion Chromatography Analysis

Size exclusion chromatography was used to determine the aggregation state of anti-CD8 alpha FN3 domain molecules. Aliquots (10 μL) of each purified FN3 domain were injected onto a Superdex 75 5/150 column (GE Healthcare) at a flow rate of 0.3 mL/min in a mobile phase of PBS pH 7.4. Elution from the column was monitored by absorbance at 280 nm. Wild-type Tencon was included in each run as a control. Agilent ChemStation software was used to analyse the elution profiles. Only those proteins with elution profiles similar to that of the tenascin consensus protein in the same run were considered for further characterization. After panning, ELISA screening and size exclusion chromatographic analysis, a total of 190 unique anti-human CD8 alpha FN3 domains were isolated that bound to recombinant human CD8 alpha greater 5 than 10-fold over background and were free of aggregates by SEC (Table 4, SEQID no. 40-228, and 70).

TABLE 4 Summary of CD8A-binding FN3 domains identified from ELISA screens Human Cyno T- T-cell Human T- cell Binding cell Binding Binding Cyno T-cell SEQ ID 2 uM 0.2 uM 2 uM Binding 0.2 Clone ID NO: (MFI) (MFI) kd (1/s) (MFI) uM (MFI) P282AR9P1356_A10 40 4258 2093 2.91E−04 10584 3122 P282AR9P1356_A4 41 16674 4380 8.61E−05 26447 8632 P282AR9P1356_A6 42 10835 3441 9.73E−05 31432 5783 P282AR9P1356_B9 43 17158 3670 2.95E−04 36397 5437 P282AR9P1356_D3 44 5963 2403 1.58E−04 13852 3365 P282AR9P1356_H1 45 14696 3234 1.14E−04 46317 5699 P282AR9P1356_H6 46 6646 2642 8.08E−05 14393 3205 P282BR9P1357_A9 47 3117 1074 5.90E−04 7281 1940 P282BR9P1357_B2 48 5931 2875 1.00E−04 17974 3841 P282BR9P1357_C10 49 9779 2901 4.58E−04 24476 5110 P282BR9P1357_C4 50 16809 4224 1.27E−04 41586 7064 P282BR9P1357_D12 51 15269 3899 8.76E−05 40450 7364 P282BR9P1357_D2 52 9606 1568 1.05E−03 25843 2525 P282BR9P1357_E5 53 6726 2587 2.10E−04 10563 4101 P282BR9P1357_G9 54 12733 2803 3.04E−04 41492 4635 P282BR9P1357_H3 55 11142 3033 2.85E−04 27090 5701 P282CR9P1358_C2 56 10086 1059 1.13E−03 55786 7047 P282CR9P1358_C5 57 2706 511 9.99E−04 25688 1831 P282CR9P1358_D10 58 28650 2764 3.11E−04 74051 4072 P282CR9P1358_F11 59 6420 749 1.35E−03 62412 6585 P282CR9P1358_F5 60 24427 3072 6.37E−04 85691 13667 P282DR9P1359_A12 61 32222 5952 8.12E−05 88032 15491 P282DR9P1359_A7 62 38382 8764 7.54E−04 83943 22803 P282DR9P1359_A8 63 21124 2113 6.38E−04 70263 7766 P282DR9P1359_B2 64 22228 2726 6.38E−04 60866 4472 P282DR9P1359_C10 65 27822 2879 9.91E−04 98481 15134 P282DR9P1359_C11 66 18176 1288 2.16E−03 19916 457 P282DR9P1359_C12 67 15106 944 9.78E−04 66538 3636 P282DR9P1359_C5 68 31017 5551 1.74E−04 95679 14183 P282DR9P1359_D12 69 4540 542 1.93E−03 37139 1746 P282DR9P1359_E11 70 40607 7578 2.65E−04 104291 33144 P282DR9P1359_E2 71 28491 4824 2.06E−03 77725 10939 P282DR9P1359_E3 72 4307 349 2.63E−03 52426 1625 P282DR9P1359_E5 73 24100 1954 1.01E−03 81183 13601 P282DR9P1359_E6 74 20507 1262 1.71E−03 61734 5065 P282DR9P1359_E8 75 26074 2919 1.19E−03 80973 16948 P282DR9P1359_F11 76 35639 6592 5.54E−04 86740 16146 P282DR9P1359_F2 77 18415 3047 7.22E−04 38228 4031 P282DR9P1359_F3 78 6343 646 1.06E−03 48861 3084 P282DR9P1359_F5 79 48931 8483 9.02E−05 113733 34709 P282DR9P1359_F6 80 19937 3782 3.89E−04 73219 10680 P282DR9P1359_F7 81 38323 6932 3.65E−04 96456 26331 P282DR9P1359_G4 82 26568 2670 5.17E−04 78619 6006 P282DR9P1359_G7 83 37626 6129 1.14E−04 69085 8769 P282DR9P1359_H5 84 919 278 4.49E−03 2252 500 P282ER9P1360_A9 85 23379 5344 1.33E−04 64694 8732 P282ER9P1360_C1 86 25874 6291 1.81E−04 64813 9679 P282ER9P1360_C4 87 19202 3459 1.07E−03 33427 3896 P282ER9P1360_C6 88 25942 5079 1.75E−04 52783 7579 P282ER9P1360_C8 89 30578 6013 1.56E−04 66829 10220 P282ER9P1360_D11 90 36755 3210 1.42E−04 76564 1937 P282ER9P1360_E4 91 26889 5030 1.91E−04 60757 6867 P282ER9P1360_F11 92 22442 3863 2.25E−04 48653 4407 P282ER9P1360_G10 93 26951 7046 2.07E−03 62701 22641 P282ER9P1360_G7 94 25438 5869 2.21E−04 69709 9921 P282ER9P1360_H10 95 2513 506 1.04E−03 27063 1887 P282ER9P1360_H2 96 15165 3479 2.69E−04 44563 4535 P282ER9P1360_H3 97 19992 4271 2.42E−04 65994 6441 P282FR9P1361_A3 98 7670 1661 7.57E−04 8476 740 P282FR9P1361_A5 99 32752 5213 1.92E−04 63541 8108 P282FR9P1361_C7 100 8538 1575 2.24E−03 11639 896 P282FR9P1361_D3 101 6881 1028 5.02E−03 14762 764 P282FR9P1361_E12 102 15794 1130 1.09E−03 63536 15052 P282FR9P1361_F1 103 5498 801 1.26E−03 9869 1392 P282FR9P1361_F11 104 2189 382 2.13E−03 2289 384 P282FR9P1361_F2 105 4610 498 4.96E−03 10883 462 P282FR9P1361_F3 106 5157 674 1.07E−02 9709 513 P282FR9P1361_F7 107 7001 1107 1.14E−03 1705 353 P282FR9P1361_G9 108 859 297 6.53E−03 3746 666 P282FR9P1361_H4 109 13056 3736 3.17E−04 26273 2504 P282FR9P1361_H5 110 5730 698 5.77E−03 11794 637 P283AR9P1362_A3 111 5535 1400 1.53E−03 17345 3533 P283AR9P1362_A4 112 6314 2539 3.02E−04 21218 4402 P283AR9P1362_B10 113 15380 3703 1.39E−04 35686 8380 P283AR9P1362_B2 114 13649 3505 1.60E−04 38828 6479 P283AR9P1362_B8 115 5737 1576 6.48E−04 12886 2271 P283AR9P1362_C12 116 7064 2616 9.94E−05 14808 3832 P283AR9P1362_C6 117 15955 4147 1.09E−03 17494 5690 P283AR9P1362_C7 118 10957 2792 1.86E−04 19690 5515 P283AR9P1362_D2 119 8650 2758 2.53E−04 17182 5333 P283AR9P1362_D3 120 9498 3484 1.25E−04 34619 6052 P283AR9P1362_D4 121 9832 2977 9.72E−05 25671 4101 P283AR9P1362_D6 122 13686 3664 2.64E−05 33547 7721 P283AR9P1362_D7 123 17327 3354 1.18E−04 27491 4849 P283AR9P1362_E9 124 6178 2010 3.27E−04 15869 2837 P283AR9P1362_F12 125 8970 2623 7.28E−05 26333 3794 P283AR9P1362_F2 126 9619 1366 2.11E−03 26443 5518 P283AR9P1362_F8 127 9195 3167 1.12E−04 23735 4571 P283AR9P1362_G11 128 12690 3531 1.02E−04 32484 6826 P283AR9P1362_G3 129 18512 4307 9.45E−05 35268 9198 P283AR9P1362_H11 130 5734 2268 1.80E−04 11588 3655 P283BR9P1363_A10 131 7886 2753 3.60E−04 27790 4105 P283BR9P1363_A8 132 11285 2536 3.53E−04 24234 3453 P283BR9P1363_B2 133 8358 2399 2.08E−04 14846 2819 P283BR9P1363_B6 134 14534 3453 2.69E−04 37691 6839 P283BR9P1363_C4 135 9073 2247 4.09E−04 23387 3266 P283BR9P1363_C8 136 16541 3739 3.35E−04 37175 9082 P283BR9P1363_D11 137 8692 2890 4.95E−04 20572 11630 P283BR9P1363_E4 138 10790 2498 3.29E−04 17702 2469 P283BR9P1363_E6 139 8239 2079 1.36E−03 16784 3715 P283BR9P1363_F2 140 14473 3274 2.88E−04 33286 5278 P283BR9P1363_F4 141 11933 2963 1.55E−04 20245 4479 P283BR9P1363_F6 142 10632 3229 8.21E−05 31568 4571 P283BR9P1363_G2 143 9640 3226 1.22E−04 15899 5383 P283BR9P1363_G5 144 14798 3307 1.40E−04 24945 4430 P283BR9P1363_G7 145 4639 2340 4.01E−05 7212 3022 P283DR9P1364_A4 146 9491 1024 1.09E−03 48337 6653 P283DR9P1364_A7 147 8985 435 1.97E−03 39870 2641 P283DR9P1364_B1 148 1477 666 1.56E−03 8617 746 P283DR9P1364_B11 149 4255 451 1.30E−03 22852 1590 P283DR9P1364_B4 150 45452 6062 1.09E−04 96492 20238 P283DR9P1364_C10 151 4936 649 1.29E−03 34234 2713 P283DR9P1364_D11 152 32293 4223 5.14E−04 70431 16240 P283DR9P1364_D8 153 656 244 6.61E−03 2484 365 P283DR9P1364_D9 154 42285 5245 4.30E−04 88300 19979 P283DR9P1364_E3 155 1285 317 2.53E−03 9128 887 P283DR9P1364_E5 156 17625 1269 8.25E−04 55654 5091 P283DR9P1364_E7 157 5394 442 2.43E−03 28732 2241 P283DR9P1364_E8 158 14321 1181 7.56E−04 59328 5510 P283DR9P1364_E9 159 4295 548 1.90E−03 19688 2096 P283DR9P1364_F2 160 39164 6252 1.61E−04 91474 16946 P283DR9P1364_F6 161 17215 1831 1.00E−03 33767 3161 P283DR9P1364_F8 162 6305 458 1.74E−03 36659 1302 P283DR9P1364_G10 163 6291 409 2.53E−03 10920 769 P283DR9P1364_G9 164 9892 401 7.79E−03 47097 2796 P283DR9P1364_H1 165 29248 3033 6.13E−04 54014 10610 P283DR9P1364_H11 166 11479 834 9.64E−04 60609 9459 P283DR9P1364_H6 167 2623 268 2.30E−03 6002 418 P283DR9P1364_H9 168 32763 4057 2.71E−04 54593 4556 P283ER9P1365_A1 169 25512 3862 4.67E−04 9676 1365 P283ER9P1365_A7 170 18513 1315 7.86E−04 36568 2960 P283ER9P1365_B6 171 22998 3397 2.88E−04 30081 2692 P283ER9P1365_C1 172 8004 644 1.15E−03 23975 1884 P283ER9P1365_E2 173 20011 2867 3.11E−04 17177 1905 P283ER9P1365_F4 174 24065 2596 2.16E−04 43243 2038 P283ER9P1365_G1 175 1280 318 3.67E−03 489 383 P283ER9P1365_G3 176 12481 2916 2.50E−03 3480 1470 P283ER9P1365_H3 177 17965 953 3.75E−04 19560 436 P283FR9P1366_A1 178 8782 516 2.26E−03 39384 1650 P283FR9P1366_A5 179 27649 3598 5.85E−04 67839 10945 P283FR9P1366_A9 180 1717 252 3.94E−03 8809 580 P283FR9P1366_B7 181 11365 899 1.15E−03 51186 4668 P283FR9P1366_C2 182 40957 4319 4.91E−04 89242 19288 P283FR9P1366_C3 183 1823 407 2.07E−03 4628 1044 P283FR9P1366_C4 184 33821 3754 5.36E−04 63373 10200 P283FR9P1366_C6 185 4541 483 1.43E−03 26242 1675 P283FR9P1366_D12 186 27793 1528 1.76E−03 87643 8143 P283FR9P1366_D6 187 32924 4554 5.09E−04 79621 10399 P283FR9P1366_D7 188 7517 566 3.54E−04 41434 2581 P283FR9P1366_D8 189 3394 413 1.34E−03 28181 2296 P283FR9P1366_E11 190 4594 567 1.41E−03 14194 1469 P283FR9P1366_F5 191 6880 720 1.04E−03 46414 4695 P283FR9P1366_F8 192 3970 369 4.03E−03 26970 2269 P283FR9P1366_F9 193 33559 6295 4.94E−04 84279 24622 P283FR9P1366_G1 194 3605 650 8.72E−04 39796 4981 P283FR9P1366_G5 195 8450 261 7.05E−04 36380 369 P283FR9P1366_G8 196 6857 574 1.08E−03 37144 3126 P283FR9P1366_H10 197 25020 2414 6.30E−04 75192 13854 P283FR9P1366_H11 198 18896 2331 1.39E−03 37386 3659 P283FR9P1366_H3 199 7671 632 1.21E−03 40770 3173 P283FR9P1366_H5 200 3137 252 3.18E−03 5091 477 P283FR9P1366_H6 201 43937 7129 2.05E−04 81542 18993 P283FR9P1366_H7 202 13778 567 1.77E−03 24435 1238 P283FR9P1366_H8 203 24942 4544 1.75E−04 61256 17144 P283FR9P1366_H9 204 8570 693 1.98E−03 36501 2877 P283GR7P1367_A11 205 11326 1029 6.35E−04 66691 5666 P283GR7P1367_B4 206 8302 446 5.18E−03 396 367 P283GR7P1367_B7 207 10865 739 1.27E−03 37518 3134 P283GR7P1367_B9 208 11242 1092 1.16E−03 2924 442 P283GR7P1367_C9 209 10989 896 2.21E−03 66977 5553 P283GR7P1367_E5 210 10014 1333 1.24E−03 3189 533 P283GR7P1367_F5 211 4565 601 1.08E−03 28950 2051 P283GR7P1367_G8 212 1463 450 3.85E−03 21031 1421 P283GR7P1367_H2 213 1621 390 2.35E−03 4207 864 P283GR7P1367_H8 214 5269 303 9.74E−03 20918 930 P283GR7P1367_H9 215 1714 434 1.47E−03 6121 918 P283HR7P1368_A10 216 13632 3233 5.13E−04 42326 4772 P283HR7P1368_B12 217 13399 1538 4.53E−05 18650 826 P283HR7P1368_C3 218 12727 2215 3.49E−04 13326 1306 P283HR7P1368_D1 219 14077 2312 1.66E−03 7850 1408 P283HR7P1368_D2 220 15246 1907 1.30E−03 11132 950 P283HR7P1368_D4 221 28979 6850 2.35E−04 52999 23549 P283HR7P1368_F10 222 18836 2661 1.65E−04 16121 1019 P283HR7P1368_F6 223 14325 3510 1.80E−04 20580 3541 P283HR7P1368_G1 224 31276 4940 2.15E−03 69817 11559 P283HR7P1368_G10 225 8122 753 1.45E−03 23790 2660 P283HR7P1368_G11 226 19305 2647 3.73E−04 14857 1343 P283HR7P1368_H1 227 15389 2460 5.52E−04 17285 1974 P283HR7P1368_H8 228 22758 1612 7.63E−04 35932 4888 Tencon25-His 270 341 219 337 336 Screen for Binding to T-Cells from Human and Cynomolgus Monkey Donors

Binding of the 190 ELISA hits to human and cynomologous monkey primary CD8 T cells was assessed by flow cytometry. The FN3 domain molecules were diluted to 2 μM and 0.2 μM in PBS and incubated with human or cynomologous monkey CD8+ T cells in 96-well format. After 1 hour at 4° C., the cells were washed once with PBS and then resuspended with an anti-FN3 domain antibody (PAB25) solution. Following this incubation, the cells were washed twice with PBS and a PE conjugated secondary antibody and a viability dye were added. Finally, cells were washed and resuspended in PBS for flow cytometric analysis using a BD Canto Instrument. Cells were gating on live cells and median fluorescence intensity of the bound Centyrins (PE channel) was calculated using Cytobank software. Results are summarized in Table 4.

Off-Rate Analysis of Anti-Human CD8 Alpha Centyrins

Purified anti-CD8A FN3 domains were subjected to off-rate analysis using a Proteon surface plasmon resonance instrument in order to pick clones with the slowest off-rates for further characterization. Measured off-rates ranged from 2.64E-5 to 1.07E-2 sec⁻¹ as shown in Table 4.

Goat anti-human Fc IgG (Jackson immunoresearch, Cat #109-005-098) was directly immobilized on a GLC sensor chip at 10 μg/ml, pH5.0 via amine coupling (pH 5.0) on all 6 ligand channels in vertical orientation on the chip with a flow rate of 30 μl/min in PBST (PBS, 0.005% Tween). The immobilized GAH-Fc IgG densities averaged about 6000 Response Units (Ru) with less than 1% variation among different channels. In house human CD8A-Fc was captured in vertical orientation at 3 different ligand densities, 10, 5, 2.5 μg/ml for 5 minutes at 30 ul/minute flowrate. All FN3 domains were normalized to a 3 μM concentration, and tested for binding in horizontal orientation. All 6 analyte channels were used for FN3 domains to maximize the screening throughput. The dissociation phase was monitored for 15 minutes at a flow rate of 100 μl/min using PBST as running buffer. Regeneration of the surface was achieved by a short pulse of 0.85% phosphoric acid (18 s contact time at 100 uL/min). Data analyses were performed using Bio-Rad ProteOn Manager software (version 3.1.0.6). Raw data were double referenced by subtraction of the interspot (empty chip surface, no protein immobilized or captured) signals to correct the non-specific binding of the FN3 domain to the pre-coated GAH-Fc IgG surface, followed by a double correction using empty channel L6 where no hCD8A-Fc was captured. The processed binding data were locally fit to a 1:1 simple Langmuir binding model to extract the koff for each FN3 domain binding to captured hCD8A-Fc.

Example 4: Engineering of Anti-CD8a FN3 Domains

A number of mutations were designed into top anti-CD8A candidates in order to eliminate post translational modification risks of oxidation (methionine, or tryptophan), deamidation (NS), isomerization (DG) and clipping (DP). Proline residues found in beta strands were also mutated as proline has a potential for destabilizing beta strands (Chiba T., et al. J Biol Chem. 2003; 278:47016-24). Only residues derived from FN3 domain library-designed positions were considered for mutation. Variant sequences were chosen to either mimic similar chemical properties of the parent molecule (example tryptophan to tyrosine) or to replace the PTM risk amino acid with an amino acid found in other CD8A FN3 domains at that position. A full list of engineered sequences is found in Table 5. The dissociation rate between each mutant and recombinant CD8 alpha was measured by surface plasmon resonance to estimate relative binding strengths.

TABLE 5 Dissociation rates of CD8A Centyrin mutants. Mutants are grouped according to the parent molecule. Sample k_(d) (1/s) Mutations SEQ ID NO: P282DR9P1359_C5 1.47E−04 Parent 68 CD8S402 4.84E−05 D40P 266 CD8S396 1.52E−04 W32Y 260 CD8S398 4.43E−04 W32S 262 CD8S397 6.60E−04 W32Q 261 CD8S399 1.34E−03 W38Y 263 CD8S401 1.27E−02 W38I 265 CD8S400 2.26E−02 W38L 264 CD8S404 3.09E−02 P36A 268 P282DR9P1359_F5 5.78E−05 Parent 79 CD8S371 1.94E−04 W48Y 235 CD8S377 4.00E−04 W81E 241 CD8S374 4.03E−04 W81Y 238 CD8S372 5.71E−04 W48L 236 CD8S375 8.30E−04 W81L 239 CD8S376 8.46E−04 W81S 240 CD8S373 4.03E−03 W48I 237 P282DR9P1359_G7 1.06E−05 83 CD8S379 4.97E−05 D43S 243 CD8S378 5.80E−05 D43E 242 CD8S388 7.54E−05 N81Q 252 CD8S387 1.25E−04 W83E 251 CD8S381 2.00E−04 W70F 245 CD8S383 7.47E−04 W74Y 247 CD8S380 1.21E−03 W70Y 244 CD8S382 2.47E−01 W70S 246 P282ER9P1360_C8 1.79E−04 Parent 89 CD8S390 1.52E−04 W68Y 254 CD8S389 1.84E−04 W68F 253 CD8S391 3.20E−04 W68H 255 CD8S405 1.14E−03 P48T 269 P282DR9P1359_F7 3.39E−04 Parent 81 CD8S403 1.33E−04 P36A 267 CD8S392 1.55E−03 W38Y 256 CD8S395 1.89E−03 W38H 259 CD8S393 2.55E−03 W38L 257 CD8S394 3.55E−03 W38I 258

From the data presented in Table 5, it is apparent that a number of mutations that reduce developability risks maintain dissociation rates similar to that of the parent molecule. Mutants CD8S402 (elimination of DP site), CD8S390 (elimination of Trp residue), and CD8S403 (removal of Pro from beta strand) resulted in slower dissociation rates than the parent appropriate molecule, indicative of tighter binding. A number of other mutations maintain binding similar to the parent molecule and thus might be preferred over the parent as these molecules pose less CMC related risks during development.

Example 5: Affinity Measurements of CD8a-Binding FN3 Domains

Nineteen anti-CD8A candidates were selected for full kinetic analysis of binding to recombinant human CD8 alpha. These candidates were selected from the above positive hits (Table 4) using the criteria of 1) strong relative binding to human T-cells, 2) strong relative binding to cyno T-cells, 3) minimal reduction in cell binding at 0.2 uM compared to 2 uM, 4) free of aggregates via SEC, 5) off-rates slower than 2.07E-3 sec-1, 6) sequence diversity with respect to sequence families, and 7) relative propensity for sequences with potential developability challenges (oxidation, deamidation, clipping and hydrophobicity).

Affinities of the top 19 candidates, later a repeat of the top 6 candidates, binding to hCD8A-Fc were measured on a ProteOn XPR36 instrument (Bio-Rad) using GLC sensor chips under similar conditions to those for koff screening. Goat anti-human Fc antibody was directly immobilized on the chip by standard amine coupling at 10 μg/ml, pH 5.0 on all 6 ligand channels in vertical orientation on the chip with a flow rate of 30 μl/min in PBST (PBS, 0.005% Tween), achieving an average of 6200 Rus on each ligand channel. Human CD8A-Fc was then captured at five surface densities ranging from 200 to 1200 response units, leaving the 6th channel as empty channel control for GAH-Fc IgG surface. Binding was measured by flowing five different concentrations of anti-CD8A FN3 domains (1 μM diluted in a 3-fold dilution series) as analytes simultaneously in the horizontal orientation over the captured hCD8A-Fc surfaces, with a sixth analyte channel containing only running buffer PBST. All interactions were measured at 100 uL/min flow rate with association and dissociation times being 4, 30 minutes respectively. Ligand surface regeneration was achieved by 1 short pulse of 0.85% phosphoric acid (18 s contact time at 100 uL/min). Data analyses were performed using Bio-Rad ProteOn Manager software (version 3.1.0.6). Raw data were double referenced by subtraction of the interspot (empty chip surface, no protein immobilized or captured) signals to correct the non-specific binding of the FN3 domain to the pre-coated GAH-Fc IgG surface, followed by a double referencing using the buffer blank response (to correct for any baseline drift resulting from ligand dissociation over time). It has been consistently observed in multiple analyses that the anti-CD8A FN3 domain binding data do not conform well to the 1:1 simple Langmuir binding model, implying either the reagents issues and/or the intrinsically complicated binding mechanisms that can't be accounted for using a simple 1:1 binding mode. Given that the GAH-Fc capture of hCD8A-Fc format is the least disruptive relative to other formats in introducing potential experimental artifacts (such as ligand activity loss and/or artificial eptiopes/heterogeneous ligand population due to amine coupling), it is considered that the results from the GAH-Fc capture experiments reported here represent the most reliable ProteOn SPR data, despite the non-conforming 1:1 Langmuir fits observed in many instances. A heterogeneous ligand model was chosen to fit the data assuming two different ligand species, either due to the heterogeneity in the ligand protein population or due to potential different mechanisms for each FN3 domain binding to the 2 hCD8A monomers in the Fc fusion protein. In this case, because each anti-CD8A FN3 domain would have separate affinities, the resultant sensorgram reflects the sum of two independent reactions with two sets of rate constants, which were reported for each FN3 domain binding.

TABLE 6 Summary of kinetic affinities for top six anti-CD8A FN3 domain candidates. Sample Lower Affinity Population Higher Affinity Population (SEQ ID NO:) k_(a) (1/Ms) k_(d) (1/s) K_(D)(nM) k_(a) (1/Ms) k_(d) (1/s) K_(D) (nM) P282DR9P1359_F5 3.48E+04 6.60E−05 6.6 3.80E+05 1.42E−05 0.04 (79) P282DR9P1359_F7 4.03E+04 3.65E−04 12 4.04E+05 7.99E−05 0.5 (81) P282DR9P1359_G7 6.84E+04 5.51E−05 2.1 2.76E+05 1.49E−05 0.05 (83) P282ER9P1360_C8 3.09E+04 9.52E−05 4.1 2.18E+05 4.71E−05 0.2 (89) P283AR9P1362_D6 5.62E+04 3.12E−05 0.98 1.55E+05 1.00E−06 0.03 (122) P282DR9P1359_C5 1.92E+04 1.27E−04 6.5 3.00E+05 5.79E−06 0.02 (68) Note: Affinity, K_(D) = kd/ka.

Example 6: Labeling of Anti-CD8a FN3 Domains with DFO and 89Zr

Anti-CD8A FN3 domains were modified to include a single cysteine residue for conjugation of maleimide containing chelators or PET labels. Synthetic plasmid DNA encoding clones P282DR9P1359_F5, P282DR9P1359_F7, P282DR9P1359_G7, P282ER9P1360_C8, P283AR9P1362_D6, and P282DR9P1359_C5 with a mutation of residue E54 to cysteine were synthesized at DNA2.0 (Table 7). E54 was chosen as the position for mutation based on earlier studies that demonstrated maintenance of binding affinity, stability, and expression levels for other FN3 domains mutated at this residue (Goldberg S. et al. Protein Engineering Design and Selection 2016 Epub ahead of print).

TABLE 7 Modified anti-CD8A FN3 domain molecules Original Clone SEQID NO Clone with E54C SEQID No P282DR9P1359_F5 79 CD8S368 229 P282DR9P1359_F7 81 CD8S367 230 P282DR9P1359_G7 83 CD8S370 231 P282ER9P1360_C8 89 CD8S365 232 P283AR9P1362_D6 122 CD8S369 233 P282DR9P1359_C5 68 CD8S366 234

Anti-CD8A FN3 domins modified with a free cysteine were conjugated to Deferoxamine (DFO) in order to chelate radiometals. 0.5 mL of a 100-500 μM anti-CD8A FN3 domain solution was combined with 10 μL of 500 mM TCEP (Sigma, cat. #646547), gently flushed with nitrogen, and incubated for 1 hour at room temperature. 1.0 mL of saturated ammonium sulfate (4.02 M) was added to each tube to reach a final concentration of 3.2M before incubation on ice for 10 minutes and centrifugation at 16,000×g or higher to pellet the protein. The resulting pellet was resuspended and washed in 1.0 mL of 3.2 M ammonium sulfate supplemented with 100 mM sodium phosphate pH 7.2 and 1 mM EDTA before centrifuging again. After the second centrifugation step, the resulting pellet was dissolved in 100 mM sodium phosphate 7. 0, 1 mM EDTA and combined with 10 uL of 50 mM DFO solution to make a final molar ratio of 5:1 DFO to anti-CD8A. This reaction was allowed to proceed at room temperature for 30 minutes before quenching with 5.0 microliters of beta-mercaptoethanol. Excess DFO was finally removed by a variety of methods including a second round of ammonium sulfate precipitation as described above, passing through a desalting column such as Zeba 7k column (Pierce Cat #89889), or by purification with nickle-NTA resin (Qiagen #30450). Anti-CD8A FN3 domain-DFO conjugates were formulated in 1×PBS for further analysis.

Following conjugation to DFO, the binding of each anti-CD8A FN3 domain to recombinant human CD8 alpha was assessed by surface plasmon resonance as previously described. All samples retained tight binding to human CD8A following mutation of E54 to Cys and conjugation to DFO (Table 8).

TABLE 8 Binding affinity following DFO conjugation Lower Affinity Population Higher Affinity Population Sample k_(a) (1/Ms) k_(d) (1/s) K_(D) (nM) k_(a) (1/Ms) k_(d) (1/s) K_(D) (nM) CD8S365-DFO 4.41E+03 4.29E−05 9.73 6.80E+04 4.18E−05 0.6 CD8S366-DFO 5.85E+03 1.06E−04 18.2 7.95E+04 7.01E−05 0.9 CD8S367-DFO 1.09E+04 9.75E−04 89.1 8.45E+04 1.31E−04 1.55 CD8S368-DFO 7.32E+03 9.98E−05 13.6 1.08E+05 2.53E−05 0.23 CD8S369-DFO 2.87E+03  ≤1E−05 ≤3.4 3.73E+04  ≤1E−05 ≤0.3 CD8S370-DFO 5.91E+03 7.65E−05 13 4.64E+04  ≤2E−05 ≤0.3

Example 7: Binding of Anti-CD8a FN3 Domains to Human and Cyno T-Cells

A full dose response binding curve was generated for the nineteen selected anti-CD8A FN3 domains. Each candidate was diluted to 20 μM in PBS followed by a 1:3 dilution series to generate either an 11-point or an 18-point dose response curve. Human or cyno CD8+ T cells were incubated with the diluted FN3 domain for 1 hour at 4° C. Cells were washed once with PBS and incubated with an anti-centyrin antibody (PAB25) for 1 hour at 4° C. The cells were washed twice with PBS, followed by incubation with a PE-secondary, anti-CD3-PacB, anti-CD4-APC, and a viability dye. Finally, cells were washed and resuspended in PBS for flow cytometric analysis using a BD Canto Instrument. CD8 T cells were defined as live CD3+CD4− cells. Median fluorescence intensity of the bound Centyrins (PE channel) and % of cells showing positive staining calculated using Cytobank software. Results were graphed using Prism and EC₅₀ values were calculated using the 4 parameter dose response variable slope equation.

A MesoScale Discovery-Cell Affinity Technology (MSD-CAT) based equilibrium cell-binding assay was performed to determine the affinity of the top six anti-CD8A candidates binding to primary human cytotoxic T cell surface CD8A receptors. Each anti-CD8A FN3 domain at a constant concentration of 50 pM was pre-incubated with 10 different concentrations of primary cytotoxic CD8 T cells (columns 2-11 in a row). Cell viability was checked prior to the binding measurements and a >85% viability was desired for valid analysis. Since these cells were from different donors, in case of donor-to-donor variations, only cells of the same donors were combined together. Each individual anti-CD8A FN3 domain binding was measured in replicates using cells from the same donors. Cells and FN3 domains were incubated overnight at 4° C. on a rotator to reach equilibrium. Following the incubation the cells were spun down along with cell bound anti-CD8A FN3 domains and the unbound (free) anti-CD8A FN3 domains in the supernatants is quantified using MSD assays where biotinylated recombinant hCD8A-Fc protein was captured at 0.6 ug/mL in assay buffer to streptavidin MSD plates overnight ˜16 hours at 4° C. After blocking the plate, supernatant with free anti-CD8A FN3 domains was added to the plate and incubated for 1 hr, then followed by SulfoTag pAb139 (In-house) detection at 1.6 ug/ml. A buffer control without any FN3 domain and hCD8A (plate background binding control) in column 1 and FN3 domain alone control without hCD8A (100% free/unbound) in column 12 were inclubed. Mouse Anti-hCD8A mAb (mIgGlk, BD Biosciences, cat #555364, clone RPA-T8) was included as a postive control. Tencon27 was included in the initial assay validation as a negative control and no significant binding was observed, and therefore, was not included in the later cell binding due to the cell availability. Plates were read immediately on the MSD Sector Imager 6000™ Reader for luminescence levels after adding MSD Read Buffer by diluting 1:4 of stock into H2O.

Raw MSD data were exported and analysed in Prism using a non-linear fit with variable slope function to derive the Bmax and Hillslope values. Only those with converged Bmax values and hillslope within the range of −1.5˜−0.5 (ideal −1.0) will be considered for further analysis. Binding data were then normalized using the Bmax values to calculate the normalized % free FN3 domains. A surface CD8 density of 50,000 receptors per cell was used for the receptor concentration calculation. A saturation criterion of <20% free Centyrin at highest CD8 cell concentrations was required to determine the affinity using a “Solution Affinity Equation for normalized data” for a 1:1 binding model.

Anti-CD8A FN3 domains bound to primary cells with affinities ranging from 0.167 to 2.81 nM (Table 9).

TABLE 9 Summary of EC₅₀ values for top six anti-CD8A FN3 domain candidates. EC50 Binding to EC50 Binding to Affinity for Clone ID Human T-cells by cyno T-cells by Human T-cells by (SEQ ID Flow Cytometry Flow Cytometry MSD-CAT NO:) (nM) (nM) (nM) CD8S365 556.0 123.6 0.167 (232) CD8S366 162.7 69.5 0.123 (234) CD8S367 194.5 50.8 0.225 (230) CD8S368 154.7 70.0 0.459 (229) CD8S369 124.2 72.3 2.81 (233) CD8S370 208.7 67.6 0.869 (231)

Example 8: Activation of Human T-Cells De Novo Activation

In order to determine if the anti-CD8A FN3 domains activate T cells, a flow cytometry assay was performed to monitor changes in T cell activation markers. Six anti-CD8A FN3 domains were evaluated for T-cell activation. De novo activation was assessed by incubating the FN3 domains at either 1 μM or 10 nM in duplicate with human pan-T cells in media for 4 days. Two independent donors were tested. Plate bound anti-CD3 was used a positive control at 2 doses, 0.1 ug/mL and 0.01 ug/mL. PBS was used as a negative control. Cells were then stained with a viability dye and the following panel of antibodies: CD4-FITC, CD3-PerCP-Cy5.5, CD69-PacB, CD45RA-BV605, CD25-BV650, CD127-PE, and CD137-PE-Cy7. CD8+ cells were defined as live CD3+CD4-cells and were profiled for each T-cell activation marker. Median fluorescence intensity values were calculated using FlowJo software and replicate values were averaged. Results are summarized in Table 10A (donor 022) and 10B (donor 146). For 365, 366, 367, 368, and 370, small changes in the T cell activation markers were observed in only 1 out of the 2 donors tested at the highest dose level of 1 μM. These changes were absent in both donors at the 10 nM dose, suggesting the molecules do not activate T cells de novo at relevant concentrations. The 369 molecule does appear to significantly activate CD137 expression in both donors at the highest dose level.

TABLE 10 Median Fluorescence Intensity (MFI) values for various T cells activation markers on CD8+ T cells for Donor 022 (A) and Donor 146 (B) Anti- Sample CD8A (SEQ ID FN3 conc Anti-CD3 CD45RA CD25 CD69 CD127 CD137 Donor NO:) μM ug/mL MFI MFI MFI MFI MFI A 022 PBS 0 0 12856 571 223 651 296 control 022 PBS 0 0.01 13133 707 403 517 343 control 022 PBS 0 0.1 11394 1333 1694 158 529 control 022 CD8S366 1 0 15054 949 477 425 310 (234) 022 CD8S366 0.01 0 13336 814 230 586 301 (234) 022 CD8S368 1 0 12992 858 698 367 329 (229) 022 CD8S368 0.01 0 15262 677 276 489 306 (229) 022 CD8S367 1 0 15409 796 401 511 297 (230) 022 CD8S367 0.01 0 13666 723 261 502 312 (230) 022 CD8S370 1 0 12946 916 572 376 353 (231) 022 CD8S370 0.01 0 14973 776 353 435 331 (231) 022 CD8S365 1 0 13935 904 562 367 328 (232) 022 CD8S365 0.01 0 15156 697 243 504 323 (232) 022 CD8S369 1 0 13661 783 440 441 5122 (233) 022 CD8S369 0.01 0 16513 717 251 596 416 (233) 022 TenCon 1 0 14920 702 284 447 334 B 146 PBS 0 0 7172 627 61 1313 500 146 PBS 0 0.01 8076 681 153 1296 617 146 PBS 0 0.1 5171 1462 1100 139 798 146 CD8S366 1 0 8531 673 95 1368 589 (234) 146 CD8S366 0.01 0 9414 623 74 1615 559 (234) 146 CD8S368 1 0 8386 691 96 1301 561 (229) 146 CD8S368 0.01 0 9147 628 82 1424 586 (229) 146 CD8S367 1 0 8167 660 95 1322 581 (230) 146 CD8S367 0.01 0 8734 586 77 1479 571 (230) 146 CD8S370 1 0 8590 737 86 1362 583 (231) 146 CD8S370 0.01 0 7934 635 71 1526 559 (231) 146 CD8S365 1 0 8344 813 85 1238 586 (232) 146 CD8S365 0.01 0 8460 628 80 1355 605 (232) 146 CD8S369 1 0 8778 681 92 1369 5690 (233) 146 CD8S369 0.01 0 7862 591 74 1498 784 (233) 146 TenCon 1 0 7325 609 78 1198 574 146 TenCon 0.01 0 7764 596 66 1281 530

Pan T-Cell Activation

In order to determine if the anti-CD8A FN3 domains can affect markers of T cell activation in pan-actived T cells, the anti-CD8A FN3 domains were also evaluated in combination with a low dose of plate bound CD3. In this assay, a sub-optimal concentration (0.01 μg/mL) of plate bound anti-CD3 was used to activate the T cells in the presence of either 1 μM or 10 nM anti-CD8A. After 4 days, the cells were assessed using the same panel and gating strategy as described above. Two independent donors were tested. Median fluorescence intensity values were calculated using FlowJo software and replicate values were averaged. Results are summarized in Tables 11A (donor 022) and 11B (donor 146).

TABLES 11A and B Median Fluorescence Intensity (MFI) values for various T cells activation markers on CD8+ T cells for Donor 022 (A) and Donor 146 (B) in the presence of plate bound CD3. A Anti- Sample CD8A (SEQ ID FN3 Anti-CD3 CD45RA CD25 CD69 CD127 CD137 Donor NO:) conc μM μg/mL MFI MFI MFI MFI MFI 022 PBS 0 0 12856 571 223 651 296 control 022 PBS 0 0.01 13133 707 403 517 343 control 022 PBS 0 0.1 11394 1333 1694 158 529 control 022 CD8S366 1 0.01 11918 892 1005 369 376 (234) 022 CD8S366 0.01 0.01 13417 1068 848 384 399 (234) 022 CD8S368 1 0.01 11311 1147 1279 260 428 (229) 022 CD8S368 0.01 0.01 13441 760 599 499 348 (229) 022 CD8S367 1 0.01 13271 1135 1127 367 385 (230) 022 CD8S367 0.01 0.01 14521 960 636 483 362 (230) 022 CD8S370 1 0.01 15138 1103 890 407 378 (231) 022 CD8S370 0.01 0.01 14230 875 612 431 355 (231) 022 CD8S365 1 0.01 14395 1112 907 380 407 (232) 022 CD8S365 0.01 0.01 14006 1175 1063 297 430 (232) 022 CD8S369 1 0.01 13735 877 759 464 5457 (233) 022 CD8S369 0.01 0.01 13864 842 617 450 498 (233) 022 TenCon 1 0.01 14687 791 553 408 358 022 TenCon 0.01 0.01 13090 759 630 464 368 B Anti- Sample CD8A Anti- (SEQ ID FN3 CD3, CD45RA CD25 CD69 CD127 CD137 Donor NO:) conc μM μg/mL MFI MFI MFI MFI MFI 146 PBS 0 0 12856 571 223 651 296 control 146 PBS 0 0.01 13133 707 403 517 343 control 146 PBS 0 0.1 11394 1333 1694 158 529 control 146 CD8S366 1 0.01 6798 876 163 1095 632 (234) 146 CD8S366 0.01 0.01 8589 775 158 1077 637 (234) 146 CD8S368 1 0.01 6576 945 175 1105 662 (229) 146 CD8S368 0.01 0.01 7608 843 200 950 678 (229) 146 CD8S367 1 0.01 6447 897 173 1088 672 (230) 146 CD8S367 0.01 0.01 7899 801 175 1031 655 (230) 146 CD8S370 1 0.01 7327 992 169 1055 687 (231) 146 CD8S370 0.01 0.01 8676 790 183 946 675 (231) 146 CD8S365 1 0.01 6624 977 172 1059 670 (232) 146 CD8S365 0.01 0.01 7902 843 193 985 659 (232) 146 CD8S369 1 0.01 7660 933 165 1149 7114 (233) 146 CD8S369 0.01 0.01 7892 854 187 989 842 (233) 146 TenCon 1 0.01 8352 829 170 1026 658 146 TenCon 0.01 0.01 7627 761 185 1043 673

Cytokine Response

In order to determine if any of the changes observed in the activation markers resulting in changes in cytokine production, antigen-dependent T cell activation assays were also performed using two anti-CD8A FN3 domains. For one set of assays, either CMV reactive or M1 reactive human PBMCs were thawed and rested overnight at 37° C. in 6 well plates. The following day, the PBMCs were harvested by pipetting, counted, and plated onto IFNg Mabtech ELISpot plates in the presence or absence of 10 μg/mL peptide. 1 μM anti-CD8A FN3-DFO conjugate was added to the wells and plates were allowed to incubate at 37° C. for approximately 24 hours undisturbed. The cells were removed and the plates were washed 5 times with PBS. The supplied detection antibody was added and plates were incubated for 2 hours. The plates were again washed and the kit substrate was added to each well. Plates were developed for approximately 5 minutes before the reaction was stopped by running the plate under water. Plates were dried upside down overnight in the dark. Plates were read on the AID EliSpot Reader and spot counts were generated using the AID EliSpot Software. Results were graphed in Prism. Results are summarized in FIG. 1 . In this assay, 365-DFO does not increase the number of IFNg spots compared to media alone or non-CD8A binding TenCon control in the absence of peptide (FIG. 1A, 1C). Peptide and CD3 are included as positive controls. In the presence of peptide, the 365-DFO does not change the number of IFNg spots compared to peptide alone or peptide with non-CD8A binding tencon (FIG. 1B, 1D). Media is included as a negative control and CD3 is included as a positive control. These results suggest that the centyrin does not affect T cell activation.

To confirm these results in a longer-term assay, IFN-gamma levels were also measured in a 6-Day activation assay. For this study, CMV reactive PBMCs were incubated in triplicate with anti-CD8A FN3 domains at 1 uM in the presence or absence of 0.25 μg/mL pp65 peptide. Cells were incubated for 6 days at 37° C. At each timepoint the cells were centrifuged and supernatant was harvested. Samples were stored at −80° C. until analyzed. Thawed samples were analyzed for IFN-gamma using a single-plex Meso Scale Discovery (MSD) based ELISA. For this assay, a standard curve was prepared as per manufacturer's instructions. Samples and standards were added to pre-coated 96 well MSD plates. After a 2 hour incubation, the kit detection antibody was added. After another 2 hour incubation, plates were washed three times followed by the addition of the supplied read buffer. Plates were read on MSD Sector Imager 6000 plate reader. Raw MSD data files were analyzed against the standard curves generated using the MSD Discovery Workbench software. The analyzed data graphed using the Tibco Spotfire program. Results are summarized in FIG. 2 . In this assay, 365-DFO does not increase the secretion of IFNg into the media compared to media alone in the absence of peptide (FIG. 2A). CMV peptide is included as a positive control. In the presence of peptide, the 365-DFO also does not change the amount of IFNg secretion compared to peptide alone (FIG. 2B). Media is included as a negative control. These results suggest that the centyrin does not affect T cell activation.

Example 9: Labeling of Anti-CD8a FN3 Domains with 1124/1125

The current method to radiolabel CD8S365 with iodine-124 to produce [¹²⁴I]-IPEM CD8S 365 (Scheme 1) was adapted from literature procedures (Bioconjugate Chem. 1991, 2, 435-440; Chemistry Open 2015, 4, 174-182).

To a 1.5 mL Eppendorf vial was added, in order, Na¹²⁴I solution (≤13 μL, ≤2.5 mCi), AcOH (5 μL to acidify the solution), 1-(4-(tributylstannyl)phenethyl)-1H-pyrrole-2,5-dione (75 μL, 1.00 mg/mL in MeCN) and iodogen (5 μL, 1.00 mg/mL in MeCN) solution. The reaction was left for 5 min at room temperature.

The crude reaction mixture was diluted with 0.5 mL of 20% EtOH/H₂O and was purified directly on preparatory HPLC, the retention time=14.4 min (FIG. 3 ). The [¹²⁴I]-IPEM was collected in a 1 dram vial that had been pre-treated with Sigma-Cote′ (then rinsed with 3 mL of 70% EtOH, followed by 3 mL of H₂O); total volume collected off preparatory HPLC <750 μL.

An aliquot (˜5-25 μCi) of the purified fraction was then injected on analytical HPLC (FIG. 4 , retention time=11.7 min).

The purified [¹²⁴]-IPEM was then concentrated under vacuum at ambient temperature to a volume of <100 μL.

Sodium phosphate buffer (1.0 M sodium phosphate, 1 mM EDTA, pH=6.86) was added (≥25 μL) to bring the pH to ˜6.5-7 (checked by strip). Lastly freshly reduced CD8S 365 (c ˜4.57 mg/mL in 100 mM sodium phosphate buffer, 1 mM EDTA, pH=6.86), was added in appropriate amount to achieve targeted specific activity (ie. if targeting specific activity of 25 mCi/mg and 2.0 mCi of [¹²⁴I]-IPEM was collected add 17.5 μL of centyrin at c ˜4.57 mg/mL). The conjugation reaction was left for 60 min at ambient temperature and the reaction progress was checked to verify that the conversion exceeded 90% by iTLC.

Purification consisted of diluting the reaction solution with PBS/10% EtOH (1 mL, pH=7) transferring the reaction solution from the 1 dram vial into a Vivaspin 6 5 kDa MWCO centrifugal filter (see appendix for the pre-conditioning). After the transfer, the reaction Eppendorf was rinsed with PBS/10% EtOH (2×1 mL, pH=7) and the washings were added to the filter. The crude reaction mixture was centrifuged at 4000 rpm, at 20° C. for 30 min. Following centrifugation <500 μL of solution remained and was found to have a radiochemical purity (RCP)>95% by radio TLC (FIG. 5 ). The purified [¹²⁴I]-IPEM CD8S 365 was diluted to a volume of 500 μL with PBS/10% EtOH if the volume was <500 μL and then filtered through a Millex-GV 0.22 μm hydrophilic Durapore (PVDF) membrane.

The radiochemical yield from the protocol is ˜50% with a radiochemical purity ≥95% RCP by radio TLC). Analytical reverse phase HPLC was used to determine the protein concentration and specific activity of the final product. The average integration of the peak at retention time=7.3 min in the UV at λ=280 nm was used to extrapolate the protein concentration from a calibration curve (FIG. 6 for a representative example). A co-injection with the non-radioactive cold standard IPEM CD8S 365 (MALDI analysis shown in FIG. 7 ) was also conducted (see FIG. 8 ). The bacterial endotoxin concentration was measured using the Endosafe® portable test system using a 10× dilution with LAL reagent water.

Example 10: Detection of CD8 Expression in Cynomolgus Monkeys

Two anti-CD8A FN3 molecules (CD8S365 and CD8S368) were selected for PET imaging in non-human primates (NHP). The anti-CD8A molecules were radiolabeled with either Zr-89 (Zevacor, Somerset, N.J.) or I-124 (CPDC, Hamilton, Canada, and Zevacor, Somerset, N.J.). Approximately 1-2 mCi of radiolabeled anti-CD8A molecules was(were) injected into the saphenous vein of a female NHP (cynomolgus macaque), while anesthetized with isoflurane in oxygen. Each animal was scanned in a large-bore microPET Focus 220 PET scanner (Siemens, Knoxville, Tenn.), with the bed moved to accommodate the entire body of the animal (head to lower abdomen). Each scan lasted approximately 1 h, and scans were acquired at 15 min, 2 h, and 24 h after injection. PET images were reconstructed using a 2D maximum likelihood expectation maximization (ML-EM) algorithm, into 3D images of voxel size 1.898×1.898×0.796 mm, dimensions 128×128×475. Blood samples were obtained at multiple time points from the saphenous vein in the opposite leg to the injection, and the blood radioactivity counted in a well counter.

PET images were analyzed using PMOD v3.7 software (PMOD, Zurich, Switzerland). Regions-of-interest were drawn manually around organs such as spleen, kidneys and liver. Counts were converted to units of percent injected dose per gram of tissue (% ID/g), while blood radioactivity was presented as % ID. A representative PET image is shown in FIG. 9 .

Blood kinetics for each NHP and each anti-CD8A FN3 domain molecule (labeled with either Zr-89 or I-124) are shown in Table 11, and summarized in FIG. 10 . For the same animals and anti-CD8A molecules, the organ biodistributions are shown in Table 12 (units are % ID/g), and summarized in FIG. 11 . The Zr-89 labeled molecules exhibited residualization of the radioisotope in the excretory organs, which caused a large background signal in the kidneys, potentially obscuring other nearby tissues. This was largely absent from the I-124 labeled molecules. The spleen uptake was very similar between the two different molecules and two different radioisotopes for all time points.

TABLE 11 Blood kinetics for each centyrin, radiolabeled with either Zr-89 or I-124 (entries are % ID). Time (h) 365 Zr-89 Time (h) 368 Zr-89 Time (h) 365 I-124 Time (h) 368 I-124 0.38 32.49 0.25 75.64 0.40 73.53 0.33 50.56 0.62 17.62 0.50 44.01 0.65 44.59 0.57 37.07 1.18 9.03 0.75 32.06 0.92 29.79 0.87 19.33 2.00 6.12 1.00 24.20 1.13 24.51 1.17 16.01 3.70 3.77 1.50 18.82 2.00 17.14 1.37 12.84 24.00 1.36 2.00 14.22 3.33 10.92 2.07 12.18 3.33 8.40 3.88 8.20 24.00 1.94 23.03 1.24 For the same animals and anti-CD8A molecules, the organ biodistributions are shown in Table 12 (units are % ID/g), and summarized in FIG. 11 .

TABLE 12 Organ uptake for the different centyrins, labeled with either Zr-89 or I-124 (entries are % ID/g). Time (h) Kidney Spleen Liver 365 Zr-89 0.25 h 0.641 0.0386 0.0620   2 h 0.624 0.0218 0.0513   24 h 0.633 0.0136 0.0354 368 Zr-89 0.25 h 0.575 0.0345 0.0740   2 h 0.664 0.0307 0.0688   24 h 0.931 0.0294 0.0508 365 I-124 0.25h 0.104 0.0324 0.0291   2 h 0.065 0.0222 0.0142   24 h Not collected due to technical issue 368 I-124 0.25 h 0.292 0.0357 0.0439   2 h 0.140 0.0271 0.0241   24 h 0.0089 0.0022 0.0029

Example 11: Specificity of Anti-CD8a FN3 Domains in Cynomolgus Monkeys

In order to test specificity of the anti-CD8A molecules, the same monkeys were treated with a chimeric CD8-depleting antibody (CM-T807 mouse V/human Fc anti-CD8 antibody) to reduce CD8+ T cells prior to imaging. Animals were administered s.c. with 10 mg/kg CD8 depleting antibody 3 days prior to imaging. CD8 depletion was confirmed by measuring the percentage of CD8 T cells in blood samples taken from each animal before and after depletion (FIG. 12 ).

Approximately 1-2 mCi of radiolabeled [I-124]CD8S365 anti-CD8 FN3 domain molecule was injected into the saphenous vein of a female NHP (cynomolgus macaque), while anesthetized with isoflurane in oxygen. Each animal was scanned in a large-bore microPET Focus 220 PET scanner (Siemens, Knoxville, Tenn.), with the bed moved to accommodate the entire body of the animal (head to lower abdomen). Each scan lasted approximately 1 h, and scans were acquired at 15 min, 2 h, and 24 h after injection. PET images were reconstructed using a 2D maximum likelihood expectation maximization (ML-EM) algorithm, into 3D images of voxel size 1.898×1.898×0.796 mm, dimensions 128×128×475. Blood samples were obtained at multiple time points from the saphenous vein in the opposite leg to the injection, and the blood radioactivity counted in a well counter.

PET images were analyzed using PMOD v3.7 software (PMOD, Zurich, Switzerland). Regions-of-interest were drawn manually around organs such as spleen, kidneys and liver. Counts were converted to units of percent injected dose per gram of tissue (% ID/g), while blood radioactivity was presented as % ID. A representative PET image is shown in FIG. 13 for a depleted animal, showing a complete absence of the spleen signal seen in the non-depleted animal in FIG. 9 .

Blood kinetics for each NHP, both depleted and non-depleted, are shown in FIG. 14 , while the organ uptakes are shown in FIG. 15 . There is little difference in blood kinetics between the depleted and non-depleted animals. Spleen uptake at the earliest time point are similar between depleted and non-depleted, since this is dominated by blood flow. However, at later time points (2 h) the spleen uptake in the depleted animals is less than half that seen in the non-depleted animals, and is essentially at background levels, demonstrating CD8A specificity of the radiolabeled centyrin.

Example 12: Sensitivity and Specificity of Pet Imaging in Cd8 Over-Expressing Tumors

In order to determine the lowest number of cells that can be detected with the anti-CD8A FN3 domain molecules and PET, a study was performed in mice using different numbers of CD8 overexpressing cells. Forty 4-5 week old female NOD-scid IL2rγ^(null) (NSG) mice (JAX Laboratory) were used, and acclimated for 7-10 days. Mice were group housed in IVC-cages under a 12-h light:dark cycle (lights on at 06:30 h) at a temperature of 19 to 22° C. Mice were fed a standard autoclaved laboratory chow and water ad libitum. Mice were ear-tagged and tails were tattooed 5-7 days prior to the start of the study to identify each animal.

HEK-293 parental and HEK-293-luc CD8+ over-expressing cell lines were maintained as 2D-cultures. Mice where implanted subcutaneously with a total of 10⁶ tumor cells in a 1:1 medium to cultrex mix containing varying ratios of HEK-293-Luc CD8+ expressing cells and HEK-293 parental cells. Once tumors were palpable, approximately 10-14 days and 200-300 mm³ in size, the human CD8+ cells were visualized using [I-124]CD8-S365.

Luciferase expression of HEK-293-Luc CD8+ cells was quantified in vivo using bioluminescence imaging in an IVIS Spectrum optical imager (Perkin Elmer). Dynamic optical imaging was performed immediately after injection of 150 mg/kg D-luciferin to identify the peak light emission.

Approximately 0.2-0.5 mCi of radiolabeled anti-CD8A FN3 domain molecules was injected into the tail vein while anesthetized with isoflurane in oxygen. Each animal was scanned in an Inveon microPET-CT scanner (Siemens, Knoxville, Tenn.) for 20 min static scan. Scans were acquired at 2-3 h post tracer injection. PET images were reconstructed using a 2D maximum likelihood expectation maximization (ML-EM) algorithm, into 3D images of voxel size 0.776×0.776×0.796 mm, dimensions 128×128×159.

PET images were analyzed using PMOD v3.7 software (PMOD, Zurich, Switzerland). Regions-of-interest were drawn manually around the tumor and other organs such as spleen, kidneys and liver. Counts were converted to units of percent injected dose per gram of tissue (% ID/g). A representative PET image is shown in FIG. 16 . Luciferase expression was quantified by drawing regions-of-interest in Living Image v4.4 software (Perkin Elmer). Light emission was measured in units of photons/sec/cm²/steradian.

Time-activity curves of radiolabeled anti-CD8A FN3 domain molecules in the blood and tumor for both CD8+ HEK293 cells and parental cells are shown in FIG. 17 and FIG. 18 . There is a significant increase in anti-CD8A FN3-binding in the CD8-expressing cells compared to the parentals, while the blood activity is the same for both. Uptake of the anti-CD8A FN3 by the CD8+ HEK293 cells is shown in FIG. 19 , as a function of number of implanted cells. Based on these data, it is estimated that the lowest level of detection is approximately 7.5×10⁶ cells.

SEQUENCE LISTING

SEQ ID No. 1 = Original Tencon Sequence LPAPKNLVVSEVTEDSLRLSWTAPDAAFDSFLIQYQESEKVGEAINLTVP GSERSYDLTGLKPGTEYTVSIYGVKGGHRSNPLSAEFTT SEQ ID No. 2 = TCL1 library LPAPKNLVVSEVTEDSLRLSWTAPDAAFDSFLIQYQESEKVGEAINLTVP GSERSYDLTGLKPGTEYTVSIYGV(X)₇₋₁₂PLSAEFTT; wherein X₁, X₂, X₃, X₄, X₅, X₆, X₇ is any amino acid; and X₈, X₉, X₁₀, X₁₁ and X₁₂ are any amino acid or deleted

SEQ ID No. 3 = TCL2 library LPAPKNLVVSEVTEDSLRLSWX₁X₂X₃X₄X₅X₆X₇X₈SFLIQYQESEKVG EAINLTVPGSERSYDLTGLKPGTEYTVSIYGVX₉X₁₀X₁₁X₁₂X₁₃SX₁₄ X₁₅LSAEFTT; wherein

X₁ is Ala, Arg, Asn, Asp, Glu, Gln, Gly, His, Ile, Leu, Lys, Phe, Pro, Ser, Thr, Trp, Tyr or Val; X₂ is Ala, Arg, Asn, Asp, Glu, Gln, Gly, His, Ile, Leu, Lys, Phe, Pro, Ser, Thr, Trp, Tyr or Val; X₃ Ala, Arg, Asn, Asp, Glu, Gln, Gly, His, Ile, Leu, Lys, Phe, Pro, Ser, Thr, Trp, Tyr or Val; X₄ is Ala, Arg, Asn, Asp, Glu, Gln, Gly, His, Ile, Leu, Lys, Phe, Pro, Ser, Thr, Trp, Tyr or Val; X₅ is Ala, Arg, Asn, Asp, Glu, Gln, Gly, His, Ile, Leu, Lys, Phe, Pro, Ser, Thr, Trp, Tyr or Val; X₆ is Ala, Arg, Asn, Asp, Glu, Gln, Gly, His, Ile, Leu, Lys, Phe, Pro, Ser, Thr, Trp, Tyr or Val; X₇ is Phe, Ile, Leu, Val or Tyr; X₈ is Asp, Glu or Thr; X₉ is Ala, Arg, Asn, Asp, Glu, Gln, Gly, His, Ile, Leu, Lys, Phe, Pro, Ser, Thr, Trp, Tyr or Val; X₁₀ is Ala, Arg, Asn, Asp, Glu, Gln, Gly, His, Ile, Leu, Lys, Phe, Pro, Ser, Thr, Trp, Tyr or Val; X₁₁ is Ala, Arg, Asn, Asp, Glu, Gln, Gly, His, Ile, Leu, Lys, Phe, Pro, Ser, Thr, Trp, Tyr or Val; X₁₂ is Ala, Arg, Asn, Asp, Glu, Gln, Gly, His, Ile, Leu, Lys, Phe, Pro, Ser, Thr, Trp, Tyr or Val; X₁₃ is Ala, Arg, Asn, Asp, Glu, Gln, Gly, His, Ile, Leu, Lys, Phe, Pro, Ser, Thr, Trp, Tyr or Val; X₁₄ is Ala, Arg, Asn, Asp, Glu, Gln, Gly, His, Ile, Leu, Lys, Phe, Pro, Ser, Thr, Trp, Tyr or Val; and X₁₅ is Ala, Arg, Asn, Asp, Glu, Gln, Gly, His, Ile, Leu, Lys, Phe, Pro, Ser, Thr, Trp, Tyr or Val.

SEQ ID No. 4 = Stabilized Tencon (Tencon 27) LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFLIQYQESEKVGEAIVLTVP GSERSYDLTGLKPGTEYTVSIYGVKGGHRSNPLSAIFTT SEQ ID No. 5 = TCL7 (FG and BC loops) LPAPKNLVVSRVTEDSARLSWX₁X₂X₃X₄X₅X₆X₇X₈X₉FDSFLIQYQES EKVGEAIVLTVPGSERSYDLTGLKPGTEYTVSIYGVX₁₀X₁₁X₁₂X₁₃ X₁₄X₁₅X₁₆X₁₇X₁₈X₁₉SNPLSAIFTT; wherein X₁, X₂, X₃, X₄, X₅, X₆, X₁₀, X₁₁, X₁₂, X₁₃, X₁₄, X₁₅ and X₁₆ are A, D, E, F, G, H, I, K, L, N, P, Q, R, S, T, V, W or Y; and X₇, X₈, X₉, X₁₇, X₁₈ and X₁₉, are A, D, E, F, G, H, I, K, L, N, P, Q, R, S, T, V, W, Y or deleted

SEQ ID No. 6 = TCL9 (FG loop) LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFLIQYQESEKVGEAIVLTVP GSERSYDLTGLKPGTEYTVSIYGVX₁X₂X₃X₄X₅X₆X₇X₈X₉X₁₀X₁₁ X₁₂SNPLSAIFTT; wherein X₁, X₂, X₃, X₄, X₅, X₆ and X₇, is A, D, E, F, G, H, I, K, L, N, P, Q, R, S, T, V, W or Y; and X₈, X₉, X₁₀, X₁₁ and X₁₂ is A, D, E, F, G, H, I, K, L, N, P, Q, R, S, T, V, W, Y or deleted.

SEQ ID No. 7 = TCL14 library LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFX₁IX₂YX₃EX₄X₅X₆X₇GE AIVLTVPGSERSYDLTGLKPGTEYX₈VX₉IX₁₀GVKGGX₁₁X₁₂SX₁₃PL SAIFTT; wherein X₁, X₂, X₃, X₄, X₅, X₆, X₁₀, X₁₁, X₁₂ and X₁₃ are A, D, E, F, G, H, I, K, L, N, P, Q, R, S, T, V, W, Y, or M.

SEQ ID No. 8 = TCL24 Library TCL24 Library (SEQ ID NO: 8) LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFX₁IX₂YX₃EX₄X₅X₆X₇GE AIX₈LX₉VPGSERSYDLTGLKPGTEYX₁₀VX₁₁IX₁₂GVKGGX₁₃X₁₄S X₁₅PLX₁₆AX₁₇FTT; wherein X₁, X₂, X₃, X₄, X₅, X₆, X₁₀, X₁₁, X₁₂ and X₁₃ are A, D, E, F, G, H, I, K, L, N, P, Q, R, S, T, V or W.

SEQ ID No. 9 = Sloning-FOR GTGACACGGCGGTTAGAAC SEQ ID No. 10 = Sloning-REV GCCTTTGGGAAGCTTCTAAG SEQ ID No. 11 = POP2250 CGGCGGTTAGAACGCGGCTACAATTAATAC SEQ ID No. 12 = DigLigRev CATGATTACGCCAAGCTCAGAA SEQ ID No. 13 = BC9 GTGACACGGCGGTTAGAACGCGGCTACAATTAATACATAACCCCATCCCC CTGTTGACAATTAATCATCGGCTCGTATAATGTGTGGAATTGTGAGCGGA TAACAATTTCACACAGGAAACAGGATCTACCATGCTGCCGGCGCCGAAAA ACCTGGTTGTTTCTGAAGTTACCGAAGACTCTCTGCGTCTGTCTTGGNNN NNNNNNNNNNNNNNNNNNNNNNNNTTYGACTCTTTCCTGATCCAGTACCA GGAATCTGAAAAAGTTGGTGAAGCGATCAACCTGACCGTTCCGGGTTCTG AACGTTCTTACGACCTGACCGGTCTGAAACCGGGTACCGAATACACCGTT TCTATCTACGGTGTTCTTAGAAGCTTCCCAAAGGC SEQ ID No. 14 = BC8 GTGACACGGCGGTTAGAACGCGGCTACAATTAATACATAACCCCATCCCC CTGTTGACAATTAATCATCGGCTCGTATAATGTGTGGAATTGTGAGCGGA TAACAATTTCACACAGGAAACAGGATCTACCATGCTGCCGGCGCCGAAAA ACCTGGTTGTTTCTGAAGTTACCGAAGACTCTCTGCGTCTGTCTTGGNNN NNNNNNNNNNNNNNNNNNNNNTTYGACTCTTTCCTGATCCAGTACCAGGA ATCTGAAAAAGTTGGTGAAGCGATCAACCTGACCGTTCCGGGTTCTGAAC GTTCTTACGACCTGACCGGTCTGAAACCGGGTACCGAATACACCGTTTCT ATCTACGGTGTTCTTAGAAGCTTCCCAAAGGC SEQ ID No. 15 = BC7 GTGACACGGCGGTTAGAACGCGGCTACAATTAATACATAACCCCATCCCC CTGTTGACAATTAATCATCGGCTCGTATAATGTGTGGAATTGTGAGCGGA TAACAATTTCACACAGGAAACAGGATCTACCATGCTGCCGGCGCCGAAAA ACCTGGTTGTTTCTGAAGTTACCGAAGACTCTCTGCGTCTGTCTTGGNNN NNNNNNNNNNNNNNNNNNTTYGACTCTTTCCTGATCCAGTACCAGGAATC TGAAAAAGTTGGTGAAGCGATCAACCTGACCGTTCCGGGTTCTGAACGTT CTTACGACCTGACCGGTCTGAAACCGGGTACCGAATACACCGTTTCTATC TACGGTGTTCTTAGAAGCTTCCCAAAGGC SEQ ID No. 16 = BC6 GTGACACGGCGGTTAGAACGCGGCTACAATTAATACATAACCCCATCCCC CTGTTGACAATTAATCATCGGCTCGTATAATGTGTGGAATTGTGAGCGGA TAACAATTTCACACAGGAAACAGGATCTACCATGCTGCCGGCGCCGAAAA ACCTGGTTGTTTCTGAAGTTACCGAAGACTCTCTGCGTCTGTCTTGGNNN NNNNNNNNNNNNNNNTTYGACTCTTTCCTGATCCAGTACCAGGAATCTGA AAAAGTTGGTGAAGCGATCAACCTGACCGTTCCGGGTTCTGAACGTTCTT ACGACCTGACCGGTCTGAAACCGGGTACCGAATACACCGTTTCTATCTAC GGTGTTCTTAGAAGCTTCCCAAAGGC SEQ ID No. 17 = 130mer-L17A CGGCGGTTAGAACGCGGCTACAATTAATACATAACCCCATCCCCCTGTTG ACAATTAATCATCGGCTCGTATAATGTGTGGAATTGTGAGCGGATAACAA TTTCACACAGGAAACAGGATCTACCATGCTG SEQ ID No. 18 = POP222ext CGG CGG TTA GAA CGC GGC TAC AAT TAA TAC SEQ ID No. 19 = LS1114 CCA AGA CAG ACG GGC AGA GTC TTC GGT AAC GCG AGA AAC AAC CAG GTT TTT CGG CGC CGG CAG CAT GGT AGA TCC TGT TTC SEQ ID No. 20 = LS1115 CCG AAG ACT CTG CCC GTC TGT CTT GG SEQ ID No. 21 = LS1117 CAG TGG TCT CAC GGA TTC CTG GTA CTG GAT CAG GAA AGA GTC GAA SEQ ID No. 22 = SDG10 CATGCGGTCTCTTCCGAAAAAGTTGGTGAAGCGATCGTCCTGACCGTTCC GGGT SEQ ID No. 23 = SDG24 GGTGGTGAAGATCGCAGACAGCGGGTTAG SEQ ID No. 24 = POP2222 CGGCGGTTAGAACGCGGCTAC SEQ ID No. 25 = SDG28 AAGATCAGTTGCGGCCGCTAGACTAGAACCGCTGCCACCGCCGGTGGTGA AGATCGCAGAC SEQ ID No. 26 = FG12 GTGACACGGCGGTTAGAACGCGGCTACAATTAATACATAACCCCATCCCC CTGTTGACAATTAATCATCGGCTCGTATAATGTGTGGAATTGTGAGCGGA TAACAATTTCACACAGGAAACAGGATCTACCATGCTGCCGGCGCCGAAAA ACCTGGTTGTTTCTCGCGTTACCGAAGACTCTGCGCGTCTGTCTTGGACC GCGCCGGACGCGGCGTTCGACTCTTTCCTGATCCAGTACCAGGAATCTGA AAAAGTTGGTGAAGCGATCGTGCTGACCGTTCCGGGTTCTGAACGTTCTT ACGACCTGACCGGTCTGAAACCGGGTACCGAATACACCGTTTCTATCTAC GGTGTTNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNTCTAACCC GCTGTCTGCGATCTTCACCACCGGCGGTCACCATCACCATCACCATGGCA GCGGTTCTAGTCTAGCGGCCGCAACTGATCTTGGC SEQ ID No. 27 = FG11 GTGACACGGCGGTTAGAACGCGGCTACAATTAATACATAACCCCATCCCC CTGTTGACAATTAATCATCGGCTCGTATAATGTGTGGAATTGTGAGCGGA TAACAATTTCACACAGGAAACAGGATCTACCATGCTGCCGGCGCCGAAAA ACCTGGTTGTTTCTCGCGTTACCGAAGACTCTGCGCGTCTGTCTTGGACC GCGCCGGACGCGGCGTTCGACTCTTTCCTGATCCAGTACCAGGAATCTGA AAAAGTTGGTGAAGCGATCGTGCTGACCGTTCCGGGTTCTGAACGTTCTT ACGACCTGACCGGTCTGAAACCGGGTACCGAATACACCGTTTCTATCTAC GGTGTTNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNTCTAACCCGCT GTCTGCGATCTTCACCACCGGCGGTCACCATCACCATCACCATGGCAGCG GTTCTAGTCTAGCGGCCGCAACTGATCTTGGC SEQ ID No. 28 = FG10 GTGACACGGCGGTTAGAACGCGGCTACAATTAATACATAACCCCATCCCC CTGTTGACAATTAATCATCGGCTCGTATAATGTGTGGAATTGTGAGCGGA TAACAATTTCACACAGGAAACAGGATCTACCATGCTGCCGGCGCCGAAAA ACCTGGTTGTTTCTCGCGTTACCGAAGACTCTGCGCGTCTGTCTTGGACC GCGCCGGACGCGGCGTTCGACTCTTTCCTGATCCAGTACCAGGAATCTGA AAAAGTTGGTGAAGCGATCGTGCTGACCGTTCCGGGTTCTGAACGTTCTT ACGACCTGACCGGTCTGAAACCGGGTACCGAATACACCGTTTCTATCTAC GGTGTTNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNTCTAACCCGCTGTC TGCGATCTTCACCACCGGCGGTCACCATCACCATCACCATGGCAGCGGTT CTAGTCTAGCGGCCGCAACTGATCTTGGC SEQ ID No. 29 = FG9 GTGACACGGCGGTTAGAACGCGGCTACAATTAATACATAACCCCATCCCC CTGTTGACAATTAATCATCGGCTCGTATAATGTGTGGAATTGTGAGCGGA TAACAATTTCACACAGGAAACAGGATCTACCATGCTGCCGGCGCCGAAAA ACCTGGTTGTTTCTCGCGTTACCGAAGACTCTGCGCGTCTGTCTTGGACC GCGCCGGACGCGGCGTTCGACTCTTTCCTGATCCAGTACCAGGAATCTGA AAAAGTTGGTGAAGCGATCGTGCTGACCGTTCCGGGTTCTGAACGTTCTT ACGACCTGACCGGTCTGAAACCGGGTACCGAATACACCGTTTCTATCTAC GGTGTTNNNNNNNNNNNNNNNNNNNNNNNNNNNTCTAACCCGCTGTCTGC GATCTTCACCACCGGCGGTCACCATCACCATCACCATGGCAGCGGTTCTA GTCTAGCGGCCGCAACTGATCTTGGC SEQ ID No. 30 = FG8 GTGACACGGCGGTTAGAACGCGGCTACAATTAATACATAACCCCATCCCC CTGTTGACAATTAATCATCGGCTCGTATAATGTGTGGAATTGTGAGCGGA TAACAATTTCACACAGGAAACAGGATCTACCATGCTGCCGGCGCCGAAAA ACCTGGTTGTTTCTCGCGTTACCGAAGACTCTGCGCGTCTGTCTTGGACC GCGCCGGACGCGGCGTTCGACTCTTTCCTGATCCAGTACCAGGAATCTGA AAAAGTTGGTGAAGCGATCGTGCTGACCGTTCCGGGTTCTGAACGTTCTT ACGACCTGACCGGTCTGAAACCGGGTACCGAATACACCGTTTCTATCTAC GGTGTTNNNNNNNNNNNNNNNNNNNNNNNNTCTAACCCGCTGTCTGCGAT CTTCACCACCGGCGGTCACCATCACCATCACCATGGCAGCGGTTCTAGTC TAGCGGCCGCAACTGATCTTGGC SEQ ID No. 31 = FG7 GTGACACGGCGGTTAGAACGCGGCTACAATTAATACATAACCCCATCCCC CTGTTGACAATTAATCATCGGCTCGTATAATGTGTGGAATTGTGAGCGGA TAACAATTTCACACAGGAAACAGGATCTACCATGCTGCCGGCGCCGAAAA ACCTGGTTGTTTCTCGCGTTACCGAAGACTCTGCGCGTCTGTCTTGGACC GCGCCGGACGCGGCGTTCGACTCTTTCCTGATCCAGTACCAGGAATCTGA AAAAGTTGGTGAAGCGATCGTGCTGACCGTTCCGGGTTCTGAACGTTCTT ACGACCTGACCGGTCTGAAACCGGGTACCGAATACACCGTTTCTATCTAC GGTGTTNNNNNNNNNNNNNNNNNNNNNTCTAACCCGCTGTCTGCGATCTT CACCACCGGCGGTCACCATCACCATCACCATGGCAGCGGTTCTAGTCTAG CGGCCGCAACTGATCTTGGC FG loop of Tencon SEQ ID NO: 32 KGGHRSN SEQ ID No. 33 = Tcon 6 AAGAAGGAGAACCGGTATGCTGCCGGCGCCGAAAAAC SEQ ID No. 34 = Tcon5E86Ishort GAG CCG CCG CCA CCG GTT TAA TGG TGA TGG TGA TGG TGA CCA CCG GTG GTG AAG ATC GCA GAC AG CD8W7 >SEQ ID No. 35: SQFRVSPLDRTWNLGETVELKCQVLLSNPTSGCSWLFQPRGAAASPTFLL YLSQNKPKAAEGLDTQRFSGKRLGDTFVLTLSDFRRENEGYYFCSALSNS IMYFSHFVPVFLPAKPTTTPAPRPPTPAPTIASQPLSLRPEACRPAGSGS GSDYKDDDDKDKTHTCPPCPAPELLGGPSVFLFPPKPKDTLMISRTPEVT CVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTYRVVSVLTVLH QDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSRDELTK NQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKL TVDKSRWQQGNVFSCSVMHEALHNHYTQKSLSLSPGK CD8W13 >SEQ ID No 36: SQFRVSPLDRTWNLGETVELKCQVLLSNPTSGCSWLFQPRGAAASPTFLL YLSQNKPKAAEGLDTQRFSGKRLGDTFVLTLSDFRRENEGYYFCSALSNS IMYFSHFVPVFLPAKPTTTPAPRPPTPAPTIASQPLSLRPEACRPAAGGA VHTRGLDFACDGGGGSDYKDDDDKGGGGSHHHHHHDKTHTCPPCPAPELL GGPSVFLFPPKPKDTLMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVH NAKTKPREEQYNSTYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKT ISKAKGQPREPQVYTLPPSRDELTKNQVSLTCLVKGFYPSDIAVEWESNG QPENNYKTTPPVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNH YTQKSLSLSPGK mIgGK signal peptide >SEQ ID No. 37: Metdtlllwvlllwvpgstg Human Fc >SEQ ID No. 38: Dkthtcppepapellggpsvflfppkpkdtlmisrtpevtcvvvdvshed pevkfnwyvdgvevhnaktkpreeqynstyrvvsvltvlhqdwlngkeyk ckvsnkalpapiektiskakgqprepqvytlppsrdeltknqvsltclvk gfypsdiavewesngqpennykttppvldsdgsfflyskltvdksrwqqg nvfscsvmhealhnhytqkslslspgk linker sequence >SEQ ID No. 39: Ggggsdykddddkggggshhhhhh

SEQ ID Clone ID No Amino Acid Sequence P282AR9P1356_A10 40 LPAPKNLVVSRVTEDSARLSWHTATNSFDSFLIQYQESEKVGEAIVL TVPGSERSYDLTGLKPGTEYTVSIYGVDVDYNPTGRPVSSNPLSAIF TT P282AR9P1356_A4 41 LPAPKNLVVSRVTEDSARLSWVKRPNSFDSFLIQYQESEKVGEAIVL TVPGSERSYDLTGLKPGTEYTVSIYGVDVVDYEGRPRWSNPLSAIFT T P282AR9P1356_A6 42 LPAPKNLVVSRVTEDSARLSWSKTDSSFDSFLIQYQESEKVGEAIVL TVPGSERSYDLTGLKPGTEYTVSIYGVDVVYIEGNPVFSNPLSAIFT T P282AR9P1356_B9 43 LPAPKNLVVSRVTEDSARLSWPEGDRPFFDSFLIQYQESEKVGEAIV LTVPGSERSYDLTGLKPGTEYTVSIYGVDVKWEGNRPVASNPLSAIF TT P282AR9P1356_D3 44 LPAPKNLVVSRVTEDSARLSWTRHETSFDSFLIQYRESEKVGEAIVL TVPGSERSYDLTGLKPGTEYTVSIYGVVVEYDAAGNPKYSNPLSAIF TT P282AR9P1356_H1 45 LPAPKNLVVSRVTEDSARLSWIPNPSSFDSFLIQYQESEKVGEAIVL TVPGSERSYDLTGLKPGTEYTVSIYGVDVVFDPVGFPSHSNPLSAIF TT P282AR9P1356_H6 46 LPAPKNLVVSRVTEDSARLSWRKRANSFDSFLIQYQESEKVGEAIVL TVPGSERSYDLTGLKPGTEYTVSIYGVHVEYDQHGRPRWSNPLSAIF TT P282BR9P1357_A9 47 LPAPKNLVVSRVTEDSARLSWKANRTTDLHFDSFLIQYQESEKVGEA IVLTVPGSERSYDLTGLKPGTEYTVSIYGVDVQYDGQQPLYSNPLSA IFTT P282BR9P1357_B2 48 LPAPKNLVVSRVTEDSARLSWNPSEDPQRFDSFLIQYQESEKVGEAI VLTVPGSERSYDLTGLKPGTEYTVSIYGVDVKWEGNRPVASNPLSAI FTT P282BR9P1357_C10 49 LPAPKNLVVSRVTEDSARLSWWSNDNRPIFDSFLIQYQESEKVGEAI VLTVPGSERSYDLTGLKPGTEYTVSIYGVDVKWEGNRPVASNPLSAI FTT P282BR9P1357_C4 50 LPAPNNLVVSRVTEDSARLSWPFVSQNKPHFDSFLIQYQESEKVGEA IVLTVPGSERSYDLTGLKPGTEYTVSIYGVDVKWEGNRPVASNPLSA IFTT P282BR9P1357_D12 51 LPAPKNLVVSRVTEDSARLSWGQYITAFSFDSFLIQYQESEKVGEAI VLTVPGSERSYDLTGLKPGTEYTVSIYGVDVAWFQGKPTWSNPLSAI FTT P282BR9P1357_D2 52 LPAPKNLVVSRVTEDSARLSWIKDGHPRHFDSFLIQYQESEKVGEAI VLTVPGSERSYDLTGLKPGTEYTVSIYGVDVVYDRGQLISSNPLSAI FTT P282BR9P1357_E5 53 LPAPKNLVVSRVTEDSARLSWWPRKYQRPFDSFLIQYQESEKVGEAI VLTVPGSERSYDLTGLKPGTEYTVSIYGVDIEWIGNRPIASNPLSAI FTT P282BR9P1357_G9 54 LPAPKNLVVSRVTEDSARLSWPIASQIHSPFDSFLIQYQESEKVGEA IVLTVPGSERSYDLTGLKPGTEYTVSIYGVDVKYDIDSRPISSNPLS AIFTT P282BR9P1357_H3 55 LPAPKNLVVSRVTEDSARLSWKKREYQDPGFDSFLIQYQESEKVGEA IVLTVPGSERSYDLTGLKPGTEYTVSIYGVDVKWEGNRPVASNPLSA IFTT P282CR9P1358_C2 56 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFKIAYPEWPSNGEAIVL TVPGSERSYDLTGLKPGTEYAVFIWGVKGGAFSNPLSAIFTT P282CR9P1358_C5 57 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFLIAYPEWPDSGEAIVL TVPGSERSYDLTGLKPGTEYAVFIWGVKGGPLSHPLSAIFTT P282CR9P1358_D10 58 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFLISYPEYPPPGEAIVL TVPGSERSYDLTGLKPGTEYFVIIFGVKGGDTSWPLSAIFTT P282CR9P1358_F11 59 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFLIAYPEWPIFEGEAIV LTVPGSERSYDLTGLKPGTEYFVVIYGVKGGEQSSPLSAIFTT P282CR9P1358_F5 60 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFWISYPEWPPDGEAIVL TVPGSERSYDLTGLKPGTEYFVIIWGVKGGETSAPLSAIFTT P282DR9P1359_A12 61 LPAPKNLVVSRVTEDSARLSWTAPEAAFDSFQIAYPEWPPPREAIVL TVPGSERSYDLTGLKPGTEYFVVIQGVKGGEISWPLSAIFTT P282DR9P1359_A7 62 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFRIGYPELEKLGYGEAI VLTVPGSERSYDLTGLKPGTEYWVIIWGVKGGENSWPLSAIFTT P282DR9P1359_A8 63 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFRIAYPEWPVQGEAIVL TVPGSERSYDLTGLKPGTEYFVIIYGVKGGELSPPLSAIFTT P282DR9P1359_B2 64 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFWIAYTEWPIPYEEAGQ EGEAIVLTVPGSERSYDLTGLKPGTEYWVSIYGVKGGPNSQPLSAIF TT P282DR9P1359_C10 65 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFAIVYPEWPTDGEAIVL TVPGSERSYDLTGLKPGTEYAVFIWGVKGGNQSWPLSAIFTT P282DR9P1359_C11 66 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFKIAYPEFPPPGEAIVL TVPGSERSYDLTGLKPGTEYYVIIIGVKGGTDSWPLSAIFTT P282DR9P1359_C12 67 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFYISYPEWPVPGEAIVL TVPGSERSYDLTGLKPGTEYWVVIYGVKGGALSVPLSAIFTT P282DR9P1359_C5 68 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFWITYPEWPDPGGEAIV LTVPGSERSYDLTGLKPGTEYFVVIYGVKGGEIYSPLSAIFTT P282DR9P1359_D12 69 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFRIAYPETATWGEAIVL TVPGSERSYDLTGLKPGTEYFVIIYGVKGGFESAPLSAIFTT P282DR9P1359_E11 70 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFYISYPEWPPVGEAIVL TVPGSERSYDLTGLKPGTEYWVIIYGVKGGAISTPLSAIFTT P282DR9P1359_E2 71 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFNIFYPEIVTWGEAIVL TVPGSERSYDLTGLKPGTEYWVNIVGVKGGDNSWPLSAIFTT P282DR9P1359_E3 72 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFAIAYPELPLGGEAIVL TVPGSERSYDLTGLKPGTEYFVIIYGVKGGVESFPLSAIFTT P282DR9P1359_E5 73 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFAISYPEWPVPGEAIVL TVPGSERSYDLTGLKPGTEYFVIIYGVKGGLYSAPLSAIFTT P282DR9P1359_E6 74 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFWIAYPEWPVQGEAIVL TVPGSERSYDLTGLKPGTEYFVVIQGVKGGTPSWPLSAIFTT P282DR9P1359_E8 75 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFQIAYPEWPVIGEAIVL TVPGSERSYDLTGLKPGTEYWVIIQGVKGGYTSWPLSAIFTT P282DR9P1359_F11 76 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFDIFYPELPIHGEAIVL TVPGSERSYDLTGLKPGTEYWVNITGVKGGDFSWPLSAIFTT P282DR9P1359_F2 77 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFNIAYPEALHPGYGEAI VLTVPGSERSYDLTGLKPGTEYWVIIGGVKGGQKSWPLSAIFTTGGH HHDHH P282DR9P1359_F3 78 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFYITYPEWPVQGEAIVL TVPGSERSYDLTGLKPGTEYWVIIYGVKGGTESEPLSAIFTT P282DR9P1359_F5 79 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFQIAYPEWPPPGEAIVL TVPGSERSYDLTGLKPGTEYFVIIQGVKGGVESWPLSAIFTT P282DR9P1359_F6 80 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFDIAYPEWPTTGEAIVL TVPGSERSYDLTGLKPGTEYFVVIWGVKGGDHSAPLSAIFTT P282DR9P1359_F7 81 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFAIAYPEWPPQGEAIVL TVPGSERSYDLTGLKPGTEYFVVIYGVKGGSYSAPLSAIFTT P282DR9P1359_G4 82 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFEIAYPEWPPPGEAIVL TVPGSERSYDLTGLKPGPEYFVVIQGVKGGDPSFPLSAIFTTGGNHH HHH P282DR9P1359_G7 83 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFAITYIEKEHIEDGEAI VLTVPGSERSYDLTGLKPGTEYWVPIWGVKGGANSWPLSAIFTT P282DR9P1359_H5 84 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFNIAYPEALHPGYGEAI VLTVPGSERSYDLTGLKPGTEYFVVIYGVKGGTNSEPLSAIFTT P282ER9P1360_A9 85 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFGILYYEPVDSGEAITL PIPGSERSYDLTGLKPGTEYWVVITGVKGGAPSTPLGAIFTT P282ER9P1360_C1 86 LPAPKNLVVSRVTEDSARLSWTTPDAAFDSFGILYYEPVDSGEAITL PVPGSERSYDLTGLKPGTEYWVVITGVKGGAPSTPLGAIFTT P282ER9P1360_C4 87 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFGITYYEPNHGGEAISL SVPGSERSYDPTGLKPGTEYWVVITGVKGGAPSTPLGAIFTT P282ER9P1360_C6 88 LSAPKNLVVSRVTEDSARLSWTAPDAAFDSFGILYYEPVDSGEAITL PIPGSERSYDLTGLKPGTEYWVVITGVKGGAPSTPLGAIFTT P282ER9P1360_C8 89 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFGILYYEPVDSGEAITL PVPGSERSYDLTGLKPGTEYWVVITGVKGGAPSTPLGTIFTT P282ER9P1360_D11 90 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFGILYYEPVDSGEAITL PVPGSERSYDLTGLKPGTEYFVIIVGVKGGYPSIPLGAAFTT P282ER9P1360_E4 91 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFGILYYEPVDSGEAITL PVLGSERSYDLTGLKPGTEYWVVITGVKGGAPSTPLGAIFTT P282ER9P1360_F11 92 LPAPKNLVVSRVTEDSARLSWIAPDAAFDSFSIAYVEAELVGEAIQL VVPGSERSYDLTGLKPGTEYWVVILGVKGGNPSNPLGASFTT P282ER9P1360_G10 93 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFAIWYVEQHPFGEAIPL FVPGSERSYDLTGLKPGTEYTVGIRGVKGGNFSTPLIAHFTT P282ER9P1360_G7 94 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFGILYYEPVDSGEAITL PVPGSERSYDLTGLKPGTEYWVVITGVKGGAPSTPLGAILTT P282ER9P1360_H10 95 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFEIYYPEWPFAGEAIGL PVPGSERSYDLTGLKPGTEYFVVIYGVKGGELSEPLTAQFTT P282ER9P1360_H2 96 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFSIAYVEAELVGEAIQL VVPGSERSYDLTGLKPGTEYWVVILGVKGGNPSNPLGASFTTT P282ER9P1360_H3 97 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFSIAYVEAELVGEAIQL VVPGSERSYDLTGLKPGTEYWVVILGVKGGNPSNPLGASFTT P282FR9P1361_A3 98 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFDIWYAEYGYPGEAIVL TVPGSERSYDLTGLKPGTEYDVAIVGVKGGNRSYPLSAIFTT P282FR9P1361_A5 99 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFGILYYEPVDSGEAITL PVPGSERSYDLTGLKPGTEYWVVITGVKGGAPSTPLGAIFTT P282FR9P1361_C7 100 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFGIWYHEYGGDGEAIVL TVPGSERSYDLTGLKPGTEYDVAIWGVKGGDVSYPLSAIFTT P282FR9P1361_D3 101 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFDIWYAEYGYPGEAIVL TVPGSERSYDLTGLNPGTEYDVAISGVKGGPRSYPLSAIFTT P282FR9P1361_E12 102 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSLGITYWESPYAGEAIVL TVPGSERSYDLTGLKPGTEYGVFILGVKGGYPSAPLSAIFTT P282FR9P1361_F1 103 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFGIWYAEYGYSGEAIVL TVPGSERSYDLTGLKPGTEYDVAIWGVKGGVRSYPLSAIFTT P282FR9P1361_F11 104 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFGIWYREYGGSGEAIVL TVPGSERSYDLTGLKPGTEYDVAIWGVKGGVRSYPLSAIFTT P282FR9P1361_F2 105 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFDIWYAEYGYPGEAIVL TVPGSERSYDLTGLKPGTEYDVAISGIKGGPRSYPLSAIFTT P282FR9P1361_F3 106 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFDIWYAEYGYPGEAIVL TVPGSERSYDLTGLKPGTEYDVAISGAKGGPRSYPLSAIFTT P282FR9P1361_F7 107 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFPIWYREYATGEAIVLT VPGSERSYDLTGLKPGTEYDVVITGVKGGYPSYPLSAIFTT P282FR9P1361_G9 108 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFGITYWESPYAGEAIVL TVPGSERSYDLTGLKPGTEYGVFILGVKGGYPSAPLSAIFTT P282FR9P1361_H4 109 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFGIWYAEYGYSGEAIVL TVPGSERSYDLTGLKPGTEYDVAIYGVKGGSPSYPLSAIFTT P282FR9P1361_H5 110 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFDIWYAEYGYPGEAIVL TVPGSERSYDLTGLKPGTEYDVAISGVKGGPRSYPLSAIFTT P283AR9P1362_A3 111 LPAPKNLVVSRVTEDSARLSWKRIDSPFDSFLIQYQESEKVGEAIVL TVPGSERSYDLTGLKPGTEYTVSIYGVDVKYDIDSRPISSNPLSAIF TT P283AR9P1362_A4 112 LPAPKNLVVSRVTEDSARLSWIGHDSGFDSFLIQYQESEKVGEAIVL TVPGSERSYDLTGLKPGTEYTVSIYGVDVKYDIDSRPISSNPLSAIF TT P283AR9P1362_B10 113 LPAPKNLVVSRVTEDSARLSWKRRWDSFDSFLIQYQESEKVGEAIVL TVPGSERSYDLTGLKPGTEYTVSIYGVDVEWFNGLPHHSNPLSAIFT T P283AR9P1362_B2 114 LPAPKNLVVSRVTEDSARLSWAKHPNSFDSFLIQYQESEKVGEAIVL TVPGSERSYDLTGLKPGTEYTVSIYGVDVVVNELNNPLFSNPLSAIF TT P283AR9P1362_B8 115 LPAPKNLVVSRVTEDSARLSWWTSPLPFDSFLIQYQESEKVGEAIVL TVPGSERSYDLTGLKPGTEYTVSIYGVDVKYDIDSRPISSNPLSAIF TT P283AR9P1362_C12 116 LPAPKNLVVSRVTEDSARLSWAKNLHSFDSFLIQYQESEKVGEAIVL TVPGSERSYDLTGLKPGTEYTVSIYGVDVKYDIDSRPISSNPLSAIF TT P283AR9P1362_C6 117 LPAPKNLVVSRVTEDSARLSWYPSDPPFDSFLIQYQESEKVGEAIVL TVPGSERSYDLTGLKPGTEYTVSIYGVPNYHSRRSYYYSNPLSAIFT T P283AR9P1362_C7 118 LPAPKNLVVSRVTEDSARLSWVKRATSFDSFLIQYQESEKVGEAIVL TVPGSERSYDLTGLKPGTEYTVSIYGVDVRYNEGQPIWSNPLSAIFT T P283AR9P1362_D2 119 LPAPKNLVVSRVTEDSARLSWQRPKSGFFDSFLIQYQESEKVGEAIV LTVPGSERSYDLTGLKPGTEYTVSIYGVDVKYDIDSRPISSNPLSAI FTT P283AR9P1362_D3 120 LPAPKNLVVSRVTEDSARLSWPVESNAFDSFLIQYQESEKVGEAIVL TVPGSERSYDLTGLKPGTEYTVSIYGVDVEYDQHGRPRWSNPLSAIF TT P283AR9P1362_D4 121 LPAPKNLVVSRVTEDSARLSWVREHDSFDSFLIQYQESEKVGEAIVL TVPGSERSYDLTGLKPGTEYTVSIYGVDVKYDIDSRPISSNPLSAIF TT P283AR9P1362_D6 122 LPAPKNLVVSRVTEDSARLSWAKRPGAFDSFLIQYQESEKVGEAIVL TVPGSERSYDLTGLKPGTEYTVSIYGVDVKYDIDSRPISSNPLSAIF TT P283AR9P1362_D7 123 LPAPKNLVVSRVTEDSARLSWVKRATSFDSFLIQYQESEKVGEAIVL TVPGSERSYDLTGLKPGTEYTVSIYGVDVKYDIDSRPISSNPLSAIF TT P283AR9P1362_E9 124 LPAPKNLVVSRVTEDSARLSWVPSPWGFDSFLIQYQESEKVGEAIVL TVPGSERSYDLTGLKPGTEYTVSIYGVDVKYDIDSRPISSNPLSAIF TT P283AR9P1362_F12 125 LPAPKNLVVSRVTEDSARLSWARNITSFDSFLIQYQESEKVGEAIVL TVPGSERSYDLTGLKPGTEYTVSIYGVDVKYDIDSRPISSNPLSAIF TT P283AR9P1362_F2 126 LPAPKNLVVSRVTEDSARLSWRKKDHPFDSFLIQYQESEKVGEAIVL TVPGSERSYDLTGLKPGTEYTVSIYGVDVKYDIDSRPISSNPLSAIF TT P283AR9P1362_F8 127 LPAPKNLVVSRVTEDSARLSWGYYHGHFDSFLIQYQESEKVGEAIVL TVPGSERSYDLTGLKPGTEYTVSIYGVDVKWEGNRPVASNPLSAIFT T P283AR9P1362_G11 128 LPAPKNLVVSRVTEDSARLSWRKEATSFDSFLIQYQESEKVGEAIVL TVPGSERSYDLTGLKPGTEYTVSIYGVDVKYDIDSRPISSNPLSAIF TT P283AR9P1362_G3 129 LPAPKNLVVSRVTEDSARLSWVKRATSFDSFLIQYQESEKVGEAIVL TVPGSERSYDLTGLKPGTEYTVSIYGVDVKWEGNRPVASNPLSAIFT T P283AR9P1362_H11 130 LPAPKNLVVSRVTEDSARLSWPKIQGQHFDSFLIQYQESEKVGEAIV LTVPGSERSYDLTGLKPGTEYTVSIYGVDVKYDIDSRPISSNPLSAI FTT P283BR9P1363_A10 131 LPAPKNLVVSRVTEDSARLSWQRADDILPYFDSFLIQYQESEKVGEA IVLTVPGSERSYDLTGLKPGTEYTVSIYGVDVKYDIDSRPISSNPLS AIFTT P283BR9P1363_A8 132 LPAPKNLVVSRVTEDSARLSWVRSDTARFFDSFLIQYQESEKVGEAI VLTVPGSERSYDLTGLKPGTEYTVSIYGVDVKYDIDSRPISSNPLSA IFTT P283BR9P1363_B2 133 LPAPKNLVVSRVTEDSARLSWASTVDPHPRFDSFLIQYQESEKVGEA IVLTVPGSERSYDLTGLKPGTEYTVSIYGVDVKYDIDSRPISSNPLS AIFTT P283BR9P1363_B6 134 LPAPKNLVVSRVTEDSARLSWQRHSDAHPLFDSFLIQYQESEKVGEA IVLTVPGSERSYDLTGLKPGTEYTVSIYGVDVKWEGNRPVASNPLSA IFTT P283BR9P1363_C4 135 LPAPKNLVVSRVTEDSARLSWPIVNTPLHFDSFLIQYQESEKVGEAI VLTVPGSERSYDLTGLKPGTEYTVSIYGVDVQYTATGQPERSNPLSA IFTT P283BR9P1363_C8 136 LPAPKNLVVSRVTEDSARLSWAKTSDLHPLFDSFLIQYQESEKVGEA IVLTVPGSERSYDLTGLKPGTEYTVSIYGVDVKWEGNRPVASNPLSA IFTT P283BR9P1363_D11 137 LPAPKNLVVSRVTEDSARLSWNKKHDGQPTFDSFLIQYQESEKVGEA IVLTVPGSERSYDLTGLKPGTEYTVSIYGVDVVYEGSYPASSNPLSA IFTT P283BR9P1363_E4 138 LPAPKNLVVSRVTEDSARLSWIKSETSQPAFDSFLIQYQESEKVGEA IVLTVPGSERSYDLTGLKPGTEYTVSIYGVDVKWEGNRPVASNPLSA IFTT P283BR9P1363_E6 139 LPAPKNLVVSRVTEDSARLSWYARKFISPFDSFLIQYQESEKVGEAI VLTVPGSERSYDLTGLKPGTEYTVSIYGVDVKWEGNRPVASNPLSAI FTT P283BR9P1363_F2 140 LPAPKNLVVSRVTEDSARLSWYRPDNRAGAFDSFLIQYQESEKVGEA IVLTVPGSERSYDLTGLKPGTEYTVSIYGVDVKYDIDSRPISSNPLS AIFTT P283BR9P1363_F4 141 LPAPKNLVVSRVTEDSARLSWERIVQ.TPHFDSFLIQYQESEKVGEA IVLTVPGSERSYDLTGLKPGTEYTVSIYGVDVKWEGNRPVASNPLSA IFTT P283BR9P1363_F6 142 LPAPKNLVVSRVTEDSARLSWPEEAVTATSFDSFLIQYQESEKVGEA IVLTVPGSERSYDLTGLKPGTEYTVSIYGVDVKWEGNRPVASNPLSA IFTT P283BR9P1363_G2 143 LPAPKNLVVSRVTEDSARLSWPKNQTNRHFDSFLIQYQESEKVGEAI VLTVPGSERSYDLTGLKPGTEYTVSIYGVDVKWEGNRPVASNPLSAI FTT P283BR9P1363_G5 144 LPAPKNLVVSRVTEDSARLSWYRATTPAPHFDSFLIQYQESEKVGEA IVLTVPGSERSYDLTGLKPGTEYTVSIYGVDVKWEGNRPVASNPLSA IFTT P283BR9P1363_G7 145 LPAPKNLVVSRVTEDSARLSWSAKKFPRHFDSFLIQYQESEKVGEAI VLTVPGSERSYDLTGLKPGTEYTVSIYGVDVKWEGNRPVASNPLSAI FTT P283DR9P1364_A4 146 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFYIAYPEWPVQGEAIVL TVPGSERSYDLTGLKPGTEYFVIIYGVKGGDWSEPLSAIFTT P283DR9P1364_A7 147 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFRIAYPEWPVRGDAIVL TVPGSERSYDLTGLKPGTEYWVIIQGVKGGTDSFPLSAIFTT P283DR9P1364_B1 148 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFYITYPEIPLGGEAIVL TVPGSERSYDLTGLKPGTEYFVVIYGVKGGLLSSPLSAIFTT P283DR9P1364_B11 149 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFYISYPEWEQLGEAIVL TVPGSERSYDLTGLKPGTEYFVVIYGVKGGALSAPLSAIFTT P283DR9P1364_B4 150 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFAISYPEWPPPGEAIVL TVPGSERSYDLTGLKPGTEYWVIILGVKGGDQSWPLSAIFTT P283DR9P1364_C10 151 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFQIAYPEWPKDGEAIVL TVPGSERSYDLTGLKPGTEYAVFIWGVKGGVYSNPLSAIFTT P283DR9P1364_D11 152 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFDIAYPEWPPKGEAIVL TVPGSERSYDLTGLKPGTEYFVVIYGVKGGIHSAPLSAIFTT P283DR9P1364_D8 153 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFQIAYPETPIQGEAIVL TVPGSERSYDLTGLKPGTEYFVIIHGVKGGITSFPLSAIFTT P283DR9P1364_D9 154 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFGISYPEWPPLGEAIVL TVPGSERSYDLTGLKPGTEYWVIIFGVKGGERSWPLSAIFTT P283DR9P1364_E3 155 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFGIAYPELPIGGEAIVL TVPGSERSYDLTGLKPGTEYFVIIRGVKGGTLSPPLSAIFTT P283DR9P1364_E5 156 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFWISYPEWPVPGEAIVL TVPGSERSYDLTGLKPGTEYWVIIQGVKGGKLSWPLSAIFTT P283DR9P1364_E7 157 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFNIAYPEWPVRGEAIVL TVPGSERSYDLTGLKPGTEYWVIIYGVKGGDRSNPLSAIFTT P283DR9P1364_E8 158 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFSIAYPEWPVHGEAIVL TVPGSERSYDLTGLKPGTEYFVIIYGVKGGVLSEPLSAIFTT P283DR9P1364_E9 159 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFDIAYPEWPTKGEAIVL TVPGSERSYDLTGLKPGTEYFVVINGVKGGWRSFPLSAIFTT P283DR9P1364_F2 160 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFWIAYPEWPVPGEAIVL TVPGSERSYDLTGLKPGTEYFVIIQGVKGGFGSFPLSAIFTT P283DR9P1364_F6 161 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFTIAYPEREQDKWGEAI VLTVPGSERSYDLTGLKPGTEYWVIIQGVKGGRPSTPLSAILTT P283DR9P1364_F8 162 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFAIAYPEWPPGEAIVLT VPGSERSYDLTGLKPGTEYFVIIYGVKGGWTSPPLSAIFTT P283DR9P1364_G10 163 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFSIAYPEWPGSGEAIVL TVPGSERSYDLTGLKPGTEYFVVIFGVKGGSQSWPLSAIFTT P283DR9P1364_G9 164 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFGIWYPEWPVGGEAIVL TVPGSERSYDLTGLKPGTEYWVNISGVKGGEYSFPLSAIFTT P283DR9P1364_H1 165 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFQISYPEWPVHGEAIVL TVPGSERSYDLTGLKPGTEYWVIIWGVKGGRQSWPLSAIFTT P283DR9P1364_H11 166 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFDIAYPELPLGGEAIVL TVPGSERSYDLTGLKPGTEYFVIIWGVKGGDRSEPLSAIFTT P283DR9P1364_H6 167 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFIIAYPETPVRGEAIVL TVPGSERSYDLTGLKPGTEYFVIIIGVKGGQESFPLSAIFTT P283DR9P1364_H9 168 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFSISYIEYPEIPGGEAI VLTVPGSERSYDLTGLKPGTEYWVPIWGVKGGIQSWPLSAIFTT P283ER9P1365_A1 169 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFGIAYVEWWHRGEAISL PVPGSERSYDLTGLKPGTEYNVIITGVKGGIPSHPLGAIFTT P283ER9P1365_A7 170 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFYIPYWESEVYGEAIAL PVPGSERSYDLTGLKPGTEYQVSIIGVKGGVYSQPLAAIFTT P283ER9P1365_B6 171 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFGIGYAEPVVTGEAISL SVPGSERSYDLTGLKPGTEYWVVIIGVKGGINSYPLGAIFTT P283ER9P1365_C1 172 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFYIPYWESEVYGEAIAL PVTGSERSYDLTGLKPGTEYQVSIIGVKGGVYSQPLAAIFTT P283ER9P1365_E2 173 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFYIPYRESEFRGEAIAL PVPGSERSYDLTGLKPGTKYRVIIIGVKGGEFSQPLAAIFTT P283ER9P1365_F4 174 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFYIPYRESEFRGEAIAL PVPGSERSYDLTGLKPGTKYSVIIIGVKGGEFSQPLGAIFTT P283ER9P1365_G1 175 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFYIPYRESEFRGEAIAL SVPGSERSYDLTGLKPGTKYRVIIIGVKGGEFSQPLGAIFTT P283ER9P1365_G3 176 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFGISYYEWAPNGEAIQL SVPGSERSYDLTGLKPGTEYHVVIIGVKGGEPSHPLGAIFTT P283ER9P1365_H3 177 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFYIPYRESEFRGEAIAL PVPGSERSYDLTGLKPGTKYRVIIIGVKGGEFSQPLSAIFTT P283FR9P1366_A1 178 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFWITYPEWPVPGEAIVL TVPGSERSYDLTGLKPGTEYAVFIWGVKGGDASEPLSAIFTT P283FR9P1366_A5 179 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFWIAYPEWPTRGEAIVL TVPGSERSYDLTGLKPGTEYFVVIYGVKGGSPSPPLSAIFTT P283FR9P1366_A9 180 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFNIAYGEYPGPGEAIVL TVPGSERSYDLTGLKPGTEYWVPIWGVKGGELSEPLSAIFTT P283FR9P1366_B7 181 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFWITYPEWPVNGEAIVL TVPGSERSYDLTGLKPGTEYWVVIWGVKGGVESPPLSAIFTT P283FR9P1366_C2 182 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFKISYPEWPPEGEAIVL TVPGSERSYDLTGLKPGTEYAVFIWCVKGGEHSWPLSAIFTT P283FR9P1366_C3 183 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFKIAYPEWPDGGEAIVL TVPGSERSYDLTGLKPGTEYFVIIYGVKGGILSPPLSAIFTT P283FR9P1366_C4 184 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFNIAYPEWPVRGEAIVL TVPGSERSYDLTGLKPGTEYWVIIIGVKGGEDSWPLSAIFTT P283FR9P1366_C6 185 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFSIAYPEWPVYGEAIVL TVPGSERSYDLTGLKPGTEYFVVIYGVKGGNYSDPLSAIFTT P283FR9P1366_D12 186 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFDIAYPEWPLGGEAIVL TVPGSERSYDLTGLKPGTEYWVIILGVKGGDQSWPLSAIFTT P283FR9P1366_D6 187 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFNIFYPELVFPGEAIVL TVPGSERSYDLTGLKPGTEYWVNISGVKGGEHSWPLSAIFTT P283FR9P1366_D7 188 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFSIAYPELPVKGEAIVL TVPGSERSYDLTGLKPGTEYFVVIWGVKGGTYSGPLSAIFTT P283FR9P1366_D8 189 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFEIAYPEIPIAGEAIVL TVPGSERSYDLTGLKPGTEYFVIIYGVKGGDWSDPLSAIFTT P283FR9P1366_E11 190 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFDIAYPEWPVPGEAIVL TVPGSERSYDLTGLKPGTEYWVIIKGVKGGNISWPLSAIFTT P283FR9P1366_F5 191 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFDIGYPEWPIKGEAIVL TVPGSERSYDLTGLKPGTEYWVIIWGVKGGDRSEPLSAIFTT P283FR9P1366_F8 192 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFAIAYPEIAKWGEAIVL TVPGSERSYDLTGLKPGTEYFVIIYGVKGGVHSFPLSAIFTT P283FR9P1366_F9 193 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFHIFYPELPIAGEAIVL TVPGSERSYDLTGLKPGTEYWVNISGVKGGYESWPLSAIFTT P283FR9P1366_G1 194 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFYISYPELPVEGEAIVL TVPGSERSYDLTGLKPGTEYWVIIWGVKGGATSEPLSAIFTT P283FR9P1366_G5 195 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFQIAYPEYPALGEAIVL TVPGSERSYDLTGLKPGTEYFVIIIGVKGGDESFPLSAIFTT P283FR9P1366_G8 196 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFDIAYPELPIGGEAIVL TVPGSERSYDLTGLKPGTEYFVVIYGVKGGIHSAPLSAIFTT P283FR9P1366_H10 197 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFNIAYPEWPPEGEAIVL TVPGSERSYDLTGLKPGTEYFVVIYGVKGGHLSDPLSAIFTT P283FR9P1366_H11 198 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFQIQYLETAPDGEAIVL TVPGSERSYDLTGLKPGTEYYVWIPGVKGGAFSPLSAIFTT P283FR9P1366_H3 199 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFAIAYPEWPIKGEAIVL TVPGSERSYDLTGLKPGTEYWVVIYGVKGGVFSEPLSAIFTT P283FR9P1366_H5 200 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFIYIENKVNGEAIVLTV PGSERSYDLTGLKPGTEYHVTIGGVKGGTESNTLSAIFTT P283FR9P1366_H6 201 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFDIAYPEWPVTGEAIVL TVPGSERSYDLTGLKPGTEYWVIIFGVKGGERSWPLSAIFTT P283FR9P1366_H7 202 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFQIAYPEYPALGEAIVL TVPGSERSYDLTGLKPGTEYFVIIAGVKGGIQSWPLSAIFTT P283FR9P1366_H8 203 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFYISYPEWPGSGEAIVL TVPGSERSYDLTGLKPGTEYAVFIWCVKGGWLSDPLSAIFTT P283FR9P1366_H9 204 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFEIAYPEWPVNGEAIVL TVPGSERSYDLTGLKPGTEYWVVIWGVKGGVNSYPLSAIFTT P283GR7P1367_A11 205 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFDIAYPEWPTDGEAIVL TVPGSERSYDLTGLKPGTEYFVIIYGVKGGSYSEPLSAIFTT P283GR7P1367_B4 206 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFSILYYELPPSGEAIVL TVPGSERSYDLTGLKPGTEYTVSIFGVKGGDNSFPLSAIFTT P283GR7P1367_B7 207 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFDIAYPEWPTDGEAIVL TVPGSERSYDLTGLKPGTEYFVVIYGVKGGHWSYPLSAIFTT P283GR7P1367_B9 208 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFEIWYHEYHPRGEAIVL TVPSSERSYDLTGLKPGTEYDVVISGVKGGHWSYPLSAIFTT P283GR7P1367_C9 209 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFLIGYPEWPLGGEAIVL TVPGSERSYDLTGLKPGTEYWVIIYGVKGGEYSDPLSAIFTT P283GR7P1367_E5 210 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFEIWYHEYHPRGEAIVL TVPGSERSYDLTGLKPGTEYDVVISGVKGGHWSYPLSAIFTT P283GR7P1367_F5 211 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFDIAYPEWPTDGEAIVL TVPGSERSYDLTGLKPGTEYFVIIYGVKGGALSRPLSAIFTT P283GR7P1367_G8 212 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFYIAYPEYVWGGEATSL GEAIVLTVPGSERSYDLTGLKPGTEYFVVITGVKGGLGSYPLSAIFT T P283GR7P1367_H2 213 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFDIAYPEWPTDGEAIVL TVPGSERSYDLTGLKPGTEYFVVIYGVKGGGRSYPLSAIFTT P283GR7P1367_H8 214 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFSINYWEEDPAGEAIVL TVPGSERSYDLTGLKPGTEYRVLIGGVKGGHGSLPLSAIFTT P283GR7P1367_H9 215 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFDIAYPEWPTDGEAIVL TVPGSERSYDLTGLKPGTEYFVVIYGVKGGGRSAPLSAIFTT P283HR7P1368_A10 216 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFWIFYLEPFPRGEAIPL EVPGSERSYDLTGLKPGTEYSVDIRGVKGGDHSDPLWAYFTT P283HR7P1368_B12 217 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFGIGYVEFTRAGEAISL SVPGSERSYDLTGLKPGTEYHVVIIGVKGGEPSHPLGAPFTT P283HR7P1368_C3 218 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFGIGYAEPAVTGEAISL SVPGSKRSYDLTGLKPGTEYWVVIIGVKGGINSYPLGASFTT P283HR7P1368_D1 219 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFGISYYEWAPNGEAIQL SVPGSERSYDLTGLKPGTEYHVVIIGVKGGEPSHPLGAPFTT P283HR7P1368_D2 220 LPAPKNLVVSRVTEDSARLSWTAPDAAFNSFGIGYAEPAVTGEAISL SVPGSERSYDLTGLKPGTEYWVVIIGVKGGINSYPLGASFTT P283HR7P1368_D4 221 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFAIWCVEPIPEGEAIPL FVPGSERSYDLTGLKPGTEYRVGIRGVKGGTFSSPLAAPFTT P283HR7P1368_F10 222 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFYIPYRESEFRGEAIAL PVPGSERSYDLTGLKPGTKYRVIIIGVKGGEFSQPLGAIFTT P283HR7P1368_F6 223 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFGIGYIEWVHRGEAISL HVPGSERSYDLTGLKPGTEYVVAIVGVKGGEPSTPLGAPFTT P283HR7P1368_G1 224 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFLITYWEIEPEGEAIFL GVPGSERSYDLTGLKPGTEYRVQINGVKGGTISYPLFAGFTT P283HR7P1368_G10 225 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFGIAYVEWWHRGEAISL PVPGSERSYDLTGLKPGTEYWVTILGVKGGIISTPLGASFTT P283HR7P1368_G11 226 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFGIGYAEPAVTGEAISL SVPGSERSYDLTGLKPGTEYWVVIIGVKGGINSYPLGASFTT P283HR7P1368_H1 227 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFGIAYIETARWGEAISL TVPGSERSYDLTGLKPGTEYNVVIIGVKGGTPSHPLGAPFTT P283HR7P1368_H8 228 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFGITYLDPRNGEAISLN VPGSERSYDLTGLKPGTEYWVVIIGVKGGINSYPLGASFTT CD8S368 229 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFQIAYPEWPPPGEAIVL TVPGSCRSYDLTGLKPGTEYFVIIQGVKGGVESWPLSAIFTT CD8S367 230 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFAIAYPEWPPQGEAIVL TVPGSCRSYDLTGLKPGTEYFVVIYGVKGGSYSAPLSAIFTT CD8S370 231 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFAITYIEKEHIEDGEAI VLTVPGSCRSYDLTGLKPGTEYWVPIWGVKGGANSWPLSAIFTT CD8S365 232 LPAPKNLVVSRVTEDSARLSWTAPDAAFDSFGILYYEPVDSGEAITL PVPGSCRSYDLTGLKPGTEYWVVITGVKGGAPSTPLGTIFTT CD8S369 233 LPAPKNLVVSRVTEDSARLSWAKRPGAFDSFLIQYQESEKVGEAIVL TVPGSCRSYDLTGLKPGTEYTVSIYGVDVKYDIDSRPISSNPLSAIF TT CD8S366 234 LPAPKNLWSRVTEDSARLSWTAPDAAFDSFWITYPEWPDPGGEAIVL TVPGSCRSYDLTGLKPGTEYFVVIYGVKGGEIYSPLSAIFTT SEQ ID Clone No Parent Sequence CD8S371 235 P282DR9P1359_F5 LPAPKNLVVSRVTEDSARLSWTA PDAAFDSFQIAYPEYPPPGEAIV LTVPGSERSYDLTGLKPGTEYFV IIQGVKGGVESWPLSAIFTT CD8S372 236 P282DR9P1359_F5 LPAPKNLVVSRVTEDSARLSWTA PDAAFDSFQIAYPELPPPGEAIV LTVPGSERSYDLTGLKPGTEYFV IIQGVKGGVESWPLSAIFTT CD8S373 237 P282DR9P1359_F5 LPAPKNLVVSRVTEDSARLSWTA PDAAFDSFQIAYPEIPPPGEAIV LTVPGSERSYDLTGLKPGTEYFV IIQGVKGGVESWPLSAIFTT CD8S374 238 P282DR9P1359_F5 LPAPKNLVVSRVTEDSARLSWTA PDAAFDSFQIAYPEWPPPGEAIV LTVPGSERSYDLTGLKPGTEYFV IIQGVKGGVESYPLSAIFTT CD8S375 239 P282DR9P1359_F5 LPAPKNLVVSRVTEDSARLSWTA PDAAFDSFQIAYPEWPPPGEAIV LTVPGSERSYDLTGLKPGTEYFV IIQGVKGGVESLPLSAIFTT CD8S376 240 P282DR9P1359_F5 LPAPKNLVVSRVTEDSARLSWTA PDAAFDSFQIAYPEWPPPGEAIV LTVPGSERSYDLTGLKPGTEYFV IIQGVKGGVESSPLSAIFTT CD8S377 241 P282DR9P1359_F5 LPAPKNLVVSRVTEDSARLSWTA PDAAFDSFQIAYPEWPPPGEAIV LTVPGSERSYDLTGLKPGTEYFV IIQGVKGGVESEPLSAIFTT CD8S378 242 P282DR9P1359_G7 LPAPKNLVVSRVTEDSARLSWTA PDAAFDSFAITYIEKEHIEEGEA IVLTVPGSERSYDLTGLKPGTEY WVPIWGVKGGANSWPLSAIFTT CD8S379 243 P282DR9P1359_G7 LPAPKNLVVSRVTEDSARLSWTA PDAAFDSFAITYIEKEHIESGEA IVLTVPGSERSYDLTGLKPGTEY WVPIWGVKGGANSWPLSAIFTT CD8S380 244 P282DR9P1359_G7 LPAPKNLVVSRVTEDSARLSWTA PDAAFDSFAITYIEKEHIEDGEA IVLTVPGSERSYDLTGLKPGTEY YVPIWGVKGGANSWPLSAIFTT CD8S381 245 P282DR9P1359_G7 LPAPKNLVVSRVTEDSARLSWTA PDAAFDSFAITYIEKEHIEDGEA IVLTVPGSERSYDLTGLKPGTEY FVPIWGVKGGANSWPLSAIFTT CD8S382 246 P282DR9P1359_G7 LPAPKNLVVSRVTEDSARLSWTA PDAAFDSFAITYIEKEHIEDGEA IVLTVPGSERSYDLTGLKPGTEY SVPIWGVKGGANSWPLSAIFTT CD8S383 247 P282DR9P1359_G7 LPAPKNLVVSRVTEDSARLSWTA PDAAFDSFAITYIEKEHIEDGEA IVLTVPGSERSYDLTGLKPGTEY WVPIYGVKGGANSWPLSAIFTT CD8S384 248 P282DR9P1359_G7 LPAPKNLVVSRVTEDSARLSWTA PDAAFDSFAITYIEKEHIEDGEA IVLTVPGSERSYDLTGLKPGTEY WVPIFGVKGGANSWPLSAIFTT CD8S385 249 P282DR9P1359_G7 LPAPKNLVVSRVTEDSARLSWTA PDAAFDSFAITYIEKEHIEDGEA IVLTVPGSERSYDLTGLKPGTEY WVPISGVKGGANSWPLSAIFTT CD8S386 250 P282DR9P1359_G7 LPAPKNLVVSRVTEDSARLSWTA PDAAFDSFAITYIEKEHIEDGEA IVLTVPGSERSYDLTGLKPGTEY WVPIWGVKGGANSYPLSAIFTT CD8S387 251 P282DR9P1359_G7 LPAPKNLVVSRVTEDSARLSWTA PDAAFDSFAITYIEKEHIEDGEA IVLTVPGSERSYDLTGLKPGTEY WVPIWGVKGGANSEPLSAIFTT CD8S388 252 P282DR9P1359_G7 LPAPKNLVVSRVTEDSARLSWTA PDAAFDSFAITYIEKEHIEDGEA IVLTVPGSERSYDLTGLKPGTEY WVPIWGVKGGAQSWPLSAIFTT CD8S389 253 P282ER9P1360_C8 LPAPKNLVVSRVTEDSARLSWTA PDAAFDSFGILYYEPVDSGEAIT LPVPGSERSYDLTGLKPGTEYFV VITGVKGGAPSTPLGTIFTT CD8S390 254 P282ER9P1360_C8 LPAPKNLVVSRVTEDSARLSWTA PDAAFDSFGILYYEPVDSGEAIT LPVPGSERSYDLTGLKPGTEYYV VITGVKGGAPSTPLGTIFTT CD8S391 255 P282ER9P1360_C8 LPAPKNLVVSRVTEDSARLSWTA PDAAFDSFGILYYEPVDSGEAIT LPVPGSERSYDLTGLKPGTEYHV VITGVKGGAPSTPLGTIFTT CD8S392 256 P282DR9P1359_F7 LPAPKNLVVSRVTEDSARLSWTA PDAAFDSFAIAYPEYPPQGEAIV LTVPGSERSYDLTGLKPGTEYFV VIYGVKGGSYSAPLSAIFTT CD8S393 257 P282DR9P1359_F7 LPAPKNLVVSRVTEDSARLSWTA PDAAFDSFAIAYPELPPQGEAIV LTVPGSERSYDLTGLKPGTEYFV VIYGVKGGSYSAPLSAIFTT CD8S394 258 P282DR9P1359_F7 LPAPKNLVVSRVTEDSARLSWTA PDAAFDSFAIAYPEIPPQGEAIV LTVPGSERSYDLTGLKPGTEYFV VIYGVKGGSYSAPLSAIFTT CD8S395 259 P282DR9P1359_F7 LPAPKNLVVSRVTEDSARLSWTA PDAAFDSFAIAYPEHPPQGEAIV LTVPGSERSYDLTGLKPGTEYFV VIYGVKGGSYSAPLSAIFTT CD8S396 260 P282DR9P1359_C5 LPAPKNLVVSRVTEDSARLSWTA PDAAFDSFYITYPEWPDPGGEAI VLTVPGSERSYDLTGLKPGTEYF VVIYGVKGGEIYSPLSAIFTT CD8S397 261 P282DR9P1359_C5 LPAPKNLVVSRVTEDSARLSWTA PDAAFDSFQITYPEWPDPGGEAI VLTVPGSERSYDLTGLKPGTEYF VVIYGVKGGEIYSPLSAIFTT CD8S398 262 P282DR9P1359_C5 LPAPKNLVVSRVTEDSARLSWTA PDAAFDSFSITYPEWPDPGGEAI VLTVPGSERSYDLTGLKPGTEYF VVIYGVKGGEIYSPLSAIFTT CD8S399 263 P282DR9P1359_C5 LPAPKNLVVSRVTEDSARLSWTA PDAAFDSFWITYPEYPDPGGEAI VLTVPGSERSYDLTGLKPGTEYF VVIYGVKGGEIYSPLSAIFTT CD8S400 264 P282DR9P1359_C5 LPAPKNLVVSRVTEDSARLSWTA PDAAFDSFWITYPELPDPGGEAI VLTVPGSERSYDLTGLKPGTEYF VVIYGVKGGEIYSPLSAIFTT CD8S401 265 P282DR9P1359_C5 LPAPKNLVVSRVTEDSARLSWTA PDAAFDSFWITYPEIPDPGGEAI VLTVPGSERSYDLTGLKPGTEYF VVIYGVKGGEIYSPLSAIFTT CD8S402 266 P282DR9P1359_C5 LPAPKNLVVSRVTEDSARLSWTA PDAAFDSFWITYPEWPPPGGEAI VLTVPGSERSYDLTGLKPGTEYF VVIYGVKGGEIYSPLSAIFTT CD8S403 267 P282DR9P1359_F7 LPAPKNLVVSRVTEDSARLSWTA PDAAFDSFAIAYAEWPPQGEAIV LTVPGSERSYDLTGLKPGTEYFV VIYGVKGGSYSAPLSAIFTT CD8S404 268 P282DR9P1359_C5 LPAPKNLVVSRVTEDSARLSWTA PDAAFDSFWITYAEWPDPGGEAI VLTVPGSERSYDLTGLKPGTEYF VVIYGVKGGEIYSPLSAIFTT CD8S405 269 P282ER9P1360_C8 LPAPKNLVVSRVTEDSARLSWTA PDAAFDSFGILYYEPVDSGEAIT LTVPGSERSYDLTGLKPGTEYWV VITGVKGGAPSTPLGTIFTT

Tencon25 SEQ ID. No. 270 LPAPKNLVVSEVTEDSARLSWTAPDAAFDSFLIQYQESEKVGEAIVLTVP GSERSYDLTGLKPGTEYTVSIYGVKGGHRSNPLSAIFTT Cyno CD8alpha SEQ ID. NO: 271 MRNQAPGRPKGATSPPPLPTGSRAPPVAPELRAEPRPGERVMAPPVTALL LPLVLLLHAARPNQFRVSPLGRTWNLGETVELKCQVLLSNPTSGCSWLFQ PRGTAARPTFLLYLSQNKPKAAEGLDTQRFSGKRLGDTFVLTLRDFRQEN EGYYFCSALSNSIMYFSHFVPVFLPAKPTTTPAPRPPTPAPTTASQPLSL RPEACRPAAGGSVNTRGLDFACDIYIWAPLAGACGVLLLSLVITLYCNHR NRRRVCKCPRPVVKSGGKPSLSDRYV 

1. An isolated FN3 domain that specifically binds to a human CD8A protein comprising the amino acid sequence of SEQ ID NO:
 35. 2. The isolated FN3 domain of claim 1, wherein the FN3 domain cross-reacts with cynomolgus monkey CD8A protein comprising the amino acid sequence of SEQ ID NO:
 271. 3. The isolated FN3 domain of claim 2, wherein a) the FN3 domain is based on a Tencon sequence of SEQ ID NO: 1; b) the FN3 domain is based on a Tencon27 sequence of SEQ ID NO: 4; and/or c) the FN3 domain is isolated from the library comprising the sequence of SEQ ID NOs: 2, 3, 5, 6, 7 or
 8. 4. The isolated FN3 domain of claim 3, wherein the FN3 domain is conjugated to a second molecule.
 5. The isolated FN3 domain of claim 4, wherein the second molecule is a detectable label.
 6. The isolated FN3 domain of claim 5, wherein the detectable label is a radioactive isotope, magnetic beads, metallic beads, colloidal particles, a fluorescent dye, an electron-dense reagent, an enzyme, biotin, digoxigenin, or hapten.
 7. The isolated FN3 domain of claim 3, wherein the FN3 domain has a cysteine substitution at residue position 54 corresponding to SEQ ID NOs 79, 81, 83, 89, 122 and
 68. 8.-10. (canceled)
 11. The isolated FN3 domain of claim 3, wherein the FN3 domain comprises any one of the amino acid sequences of SEQ ID NOs: 40-269.
 12. The isolated FN3 domain of claim 11, further comprising a methionine at the N-terminus of the FN3 domain.
 13. The isolated FN3 domain of claim 3, wherein the FN3 domain is coupled to a half-life extending moiety.
 14. The isolated FN3 domain of claim 13, wherein the half-life extending moiety is a CD8 binding molecule, albumin, an albumin variant, an albumin binding molecule, a polyethylene glygol (PEG), CD8, CD8 variant, or at least a portion of an Fc region of an immunoglobulin.
 15. An isolated polynucleotide encoding the FN3 domain of claim
 11. 16. A vector comprising the polynucleotide of claim
 15. 17. An isolated host cell comprising the vector of claim
 16. 18. A method of producing an FN3 domain that specifically binds to a human CD8A protein, comprising culturing the isolated host cell of claim 17 under conditions such that the FN3 domain is expressed, and purifying the FN3 domain.
 19. (canceled)
 20. A diagnostic or capture agent comprising the FN3 domain of claim
 11. 21. The diagnostic or capture agent of claim 20 wherein the FN3 domain has a cysteine substitution at residue position 54 corresponding to SEQ ID NOs 79, 81, 83, 89, 122 and/or
 68. 22. The diagnostic agent of claim 21 wherein the substituted cysteine is conjugated to Zr-89 or I-124.
 23. A method of detecting CD8-expressing cells in a biological sample comprising treating the biological sample with the diagnostic reagent of claim 20 and evaluating the binding of the biological sample to the FN3 domain of such diagnostic agent.
 24. The method of claim 23 wherein the diagnostic agent has a cysteine substitution at residue position 54 of SEQ ID NOs 79, 81, 83, 89, 122 and/or 68 and the substituted cysteine is conjugated to Zr-89 or I-124. 